Minor fixes

backtracking/generate_paranthesis.rb

@@ -37,7 +37,7 @@
 # @return {String[]}
 def generate_parenthesis(n)
   parenthesis = []
-  backtrack(parenthesis, "", 0, 0, n)
+  backtrack(parenthesis, '', 0, 0, n)
   parenthesis
 end
 
@@ -47,13 +47,9 @@ def backtrack(parenthesis, curr, open, close, max)
     return
   end
 
-  if open < max
+  backtrack(parenthesis, curr + '(', open + 1, close, max) if open < max
-    backtrack(parenthesis, curr + "(", open + 1, close, max)
-  end
 
-  if close < open
+  backtrack(parenthesis, curr + ')', open, close + 1, max) if close < open
-    backtrack(parenthesis, curr + ")", open, close + 1, max)
-  end
 end
 
 n = 3

bit_manipulation/binary_and_operator.rb

@@ -1,12 +1,12 @@
 def binary_and(x, y)
-  raise 'Input must only contain positive integers' if x < 0 or y < 0
+  raise 'Input must only contain positive integers' if (x < 0) || (y < 0)
 
-  "0b" + (x & y).to_s(2)
+  '0b' + (x & y).to_s(2)
 end
 
 begin
   binary_and(-1, 0)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # Input must only contain positive integers

bit_manipulation/binary_count_setbits.rb

@@ -8,7 +8,7 @@ end
 
 begin
   binary_count_setbits(-1)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # Input must be a positive integer

bit_manipulation/binary_count_trailing_zeroes.rb

@@ -5,7 +5,7 @@ def binary_count_trailing_zeroes(x)
 
   count = 0
   binary.chars.reverse_each do |char|
-    break if char == "1"
+    break if char == '1'
 
     count += 1
   end
@@ -15,7 +15,7 @@ end
 
 begin
   binary_count_trailing_zeroes(-1)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # Input must be a positive integer
@@ -32,5 +32,5 @@ puts binary_count_trailing_zeroes(1024)
 puts binary_count_trailing_zeroes(54)
 # 1
 
-puts binary_count_trailing_zeroes(121024)
+puts binary_count_trailing_zeroes(121_024)
 # 6

bit_manipulation/binary_or_operator.rb

@@ -1,12 +1,12 @@
 def binary_or(x, y)
-  raise 'Input must only contain positive integers' if x < 0 or y < 0
+  raise 'Input must only contain positive integers' if (x < 0) || (y < 0)
 
-  "0b" + (x | y).to_s(2)
+  '0b' + (x | y).to_s(2)
 end
 
 begin
   binary_or(-1, 0)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # Input must only contain positive integers
@@ -21,4 +21,3 @@ puts binary_or(0, 1023)
 # 0b1111111111
 puts binary_or(16, 58)
 # 0b110010
-

bit_manipulation/binary_xor_operator.rb

@@ -1,24 +1,24 @@
 def binary_xor(x, y)
-  raise 'Input must only contain positive integers' if x < 0 or y < 0
+  raise 'Input must only contain positive integers' if (x < 0) || (y < 0)
 
   binary_x = x.to_s(2)
   binary_y = y.to_s(2)
 
   if binary_x.length > binary_y.length
-    prefix = "0" * (binary_x.length - binary_y.length)
+    prefix = '0' * (binary_x.length - binary_y.length)
     binary_y = prefix + binary_y
   elsif binary_y.length > binary_x.length
-    prefix = "0" * (binary_y.length - binary_x.length)
+    prefix = '0' * (binary_y.length - binary_x.length)
     binary_x = prefix + binary_x
   end
-  result = "0b"
+  result = '0b'
   binary_x.each_char.with_index do |x_char, i|
     y_char = binary_y[i]
 
-    if (x_char == "1" && y_char != "1") || (x_char != "1" && y_char == "1")
+    result += if (x_char == '1' && y_char != '1') || (x_char != '1' && y_char == '1')
-      result += "1"
+                '1'
               else
-      result += "0"
+                '0'
               end
   end
 
@@ -27,7 +27,7 @@ end
 
 begin
   binary_xor(-1, 0)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # Input must only contain positive integers

bit_manipulation/single_bit_binary_operations.rb

@@ -1,5 +1,5 @@
 def set_bit(x, position)
-  raise "position must be >= 0" if position < 0
+  raise 'position must be >= 0' if position < 0
 
   x | (1 << position)
 end
@@ -18,14 +18,13 @@ puts set_bit(8, 4)
 
 begin
   puts set_bit(8, -4)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # position must be >= 0
 
-
 def clear_bit(x, position)
-  raise "position must be > 0" if position < 0
+  raise 'position must be > 0' if position < 0
 
   x & ~(1 << position)
 end
@@ -44,13 +43,13 @@ puts clear_bit(24, 4)
 
 begin
   puts clear_bit(0, -4)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # position must be > 0
 
 def flip_bit(x, position)
-  raise "position must be > 0" if position < 0
+  raise 'position must be > 0' if position < 0
 
   x ^ (1 << position)
 end
@@ -69,13 +68,13 @@ puts flip_bit(24, 4)
 
 begin
   puts flip_bit(0, -4)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # position must be > 0
 
 def is_bit_set(x, position)
-  raise "position must be > 0" if position < 0
+  raise 'position must be > 0' if position < 0
 
   ((x >> position) & 1) == 1
 end
@@ -94,7 +93,7 @@ puts is_bit_set(24, 4)
 
 begin
   puts is_bit_set(0, -4)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 # position must be > 0

conversions/temperature_conversions.rb

@@ -5,48 +5,48 @@ module TemperatureConversion
   def self.celsius_to_kelvin(celsius_input)
     kelvin_output = (celsius_input + 273.15).round(2)
     puts "#{celsius_input}°C = #{kelvin_output}K"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 
   # kelvin -> celsius = vale of kelvin - 273.15 => °C
   def self.kelvin_to_celsius(kelvin_input)
     celsius_output = (kelvin_input - 273.15).round(2)
     puts "#{kelvin_input}K = #{celsius_output}°C"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 
   # celsius -> fahrenheit = (value of celsius * 9 / 5) + 32 => °F
   def self.celsius_to_fahrenheit(celsius_input)
     fahrenheit_output = ((celsius_input * 9 / 5) + 32).round(2)
     puts "#{celsius_input}°C = #{fahrenheit_output}°F"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 
   # fahrenheit -> celsius = (value of fahrenheit - 32) * 5 / 9 => °C
   def self.fahrenheit_to_celsius(fahrenheit_input)
     celsius_output = ((fahrenheit_input - 32) * 5 / 9).round(2)
     puts "#{fahrenheit_input}°F = #{celsius_output}°C"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 
   # fahrenheit -> kelvin = [(value of fahrenheit - 32) * 5 / 9] + 273.15 => K
   def self.fahrenheit_to_kelvin(fahrenheit_input)
     kelvin_output = ((fahrenheit_input - 32) * 5 / 9).round(2).round(2)
     puts "#{fahrenheit_input}°F = #{kelvin_output}K"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 
   # kelvin -> fahrenheit = [(value of kelvin - 32) * 5 / 9] + 273.15 => K
   def self.kelvin_to_fahrenheit(kelvin_input)
     fahrenheit_output = (((kelvin_input - 273.15) * 9 / 5) + 32).round(2).round(2)
     puts "#{kelvin_input}K = #{fahrenheit_output}°F"
-  rescue
+  rescue StandardError
-    puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 end
 
@@ -55,18 +55,18 @@ TemperatureConversion.celsius_to_kelvin(20)
 TemperatureConversion.kelvin_to_celsius(20)
 
 # Invalid input
-TemperatureConversion.kelvin_to_celsius("a")
+TemperatureConversion.kelvin_to_celsius('a')
 
 # celsius <-> fahrenheit
 TemperatureConversion.celsius_to_fahrenheit(-20)
 TemperatureConversion.fahrenheit_to_celsius(68)
 
 # Invalid input
-TemperatureConversion.celsius_to_fahrenheit("abc")
+TemperatureConversion.celsius_to_fahrenheit('abc')
 
 # fahrenheit <-> kelvin
 TemperatureConversion.fahrenheit_to_kelvin(60)
 TemperatureConversion.kelvin_to_fahrenheit(-60)
 
 # Invalid input
-TemperatureConversion.fahrenheit_to_kelvin("60")
+TemperatureConversion.fahrenheit_to_kelvin('60')

conversions/weight_conversions.rb

@@ -3,7 +3,7 @@
 module WeightConversion
   # Kilogram -> Gram = (kilogram_value * 1000) grams
   def self.kilogram_to_gram(kilogram_input)
-    raise StandardError unless Integer === kilogram_input
+    raise StandardError unless kilogram_input.is_a?(Integer)
 
     gram = kilogram_input * 1000
 
@@ -40,7 +40,7 @@ module WeightConversion
 
   # Pound -> Kilogram = (pound_input / 2.205) kg
   def self.pound_to_kilogram(pound_input)
-    raise StandardError unless Integer === pound_input
+    raise StandardError unless pound_input.is_a?(Integer)
 
     kilogram = (pound_input / 2.205).round(2)
 
@@ -70,37 +70,37 @@ puts WeightConversion.pound_to_kilogram(100)
 #
 
 begin
-  puts WeightConversion.kilogram_to_gram("a")
+  puts WeightConversion.kilogram_to_gram('a')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 begin
-  puts WeightConversion.kilogram_to_gram("3000")
+  puts WeightConversion.kilogram_to_gram('3000')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 begin
-  puts WeightConversion.kilogram_to_gram("16")
+  puts WeightConversion.kilogram_to_gram('16')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 begin
-  puts WeightConversion.kilogram_to_gram("x ")
+  puts WeightConversion.kilogram_to_gram('x ')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 begin
-  puts WeightConversion.kilogram_to_gram("weight")
+  puts WeightConversion.kilogram_to_gram('weight')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 begin
-  puts WeightConversion.kilogram_to_gram("100")
+  puts WeightConversion.kilogram_to_gram('100')
 rescue StandardError
-  puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end

data_structures/arrays/add_digits.rb

@@ -20,9 +20,7 @@
 # Time complexity: O(n)
 #
 def add_digits(num)
-  if num.to_s.length < 2
+  return num if num.to_s.length < 2
-    return num
-  end
 
   digits_to_sum = num.to_s.split('')
   sum = 0

data_structures/arrays/good_pairs.rb

@@ -19,9 +19,8 @@ def num_identical_pairs(nums)
     target = num
     nums.each_with_index do |num, j|
       next if i >= j
-      if num == target
+
-        count += 1
+      count += 1 if num == target
-      end
     end
   end
   count

data_structures/arrays/intersection.rb

@@ -25,6 +25,7 @@ def intersect(arr1, arr2)
   shorter.each do |matcher|
     longer.each do |number|
       next if number != matcher
+
       result.push(number)
       break
     end
@@ -60,7 +61,7 @@ def intersect(arr1, arr2)
 
   hash = Hash.new(0)
 
-  arr2.each {|num| hash[num] += 1 }
+  arr2.each { |num| hash[num] += 1 }
 
   arr1.each do |num|
     if hash.has_key?(num)

data_structures/arrays/remove_elements.rb

@@ -19,13 +19,13 @@
 # Time complexity: O(n)
 #
 def remove_elements(nums, val)
-  nums.delete_if{ |num| num == val }
+  nums.delete_if { |num| num == val }
   nums.length
 end
 
-puts remove_elements([3,2,2,3], 3)
+puts remove_elements([3, 2, 2, 3], 3)
 # => 2
-puts remove_elements([0,1,2,2,3,0,4,2], 2)
+puts remove_elements([0, 1, 2, 2, 3, 0, 4, 2], 2)
 # => 5
 
 #
@@ -37,20 +37,20 @@ def remove_elements(nums, val)
   result_length = nums.length
   shift_length = 0
   nums.each_with_index do |num, i|
-    if num == val
+    next unless num == val
+
     nums.delete_at(i)
     nums.unshift('removed')
-      result_length -=1
+    result_length -= 1
     shift_length += 1
   end
-  end
   nums.shift(shift_length)
   result_length
 end
 
-puts remove_elements([3,2,2,3], 3)
+puts remove_elements([3, 2, 2, 3], 3)
 # => 2
-puts remove_elements([0,1,2,2,3,0,4,2], 2)
+puts remove_elements([0, 1, 2, 2, 3, 0, 4, 2], 2)
 # => 5
 
 #
@@ -78,9 +78,9 @@ def remove_element(nums, val)
   pointer1
 end
 
-puts remove_elements([3,2,2,3], 3)
+puts remove_elements([3, 2, 2, 3], 3)
 # => 2
-puts remove_elements([0,1,2,2,3,0,4,2], 2)
+puts remove_elements([0, 1, 2, 2, 3, 0, 4, 2], 2)
 # => 5
 
 #
@@ -111,7 +111,7 @@ def remove_element(nums, val)
   pointer1
 end
 
-puts remove_elements([3,2,2,3], 3)
+puts remove_elements([3, 2, 2, 3], 3)
 # => 2
-puts remove_elements([0,1,2,2,3,0,4,2], 2)
+puts remove_elements([0, 1, 2, 2, 3, 0, 4, 2], 2)
 # => 5

data_structures/arrays/richest_customer_wealth.rb

@@ -45,12 +45,12 @@ def find_richest_customer_wealth(accounts)
     summed_accounts.push(summed)
   end
 
-  summed_accounts.sort.pop()
+  summed_accounts.sort.pop
 end
 
-puts find_richest_customer_wealth([[1,2,3],[3,2,1]])
+puts find_richest_customer_wealth([[1, 2, 3], [3, 2, 1]])
 # => 6
-puts find_richest_customer_wealth([[1,5],[7,3],[3,5]])
+puts find_richest_customer_wealth([[1, 5], [7, 3], [3, 5]])
 # => 10
-puts find_richest_customer_wealth([[2,8,7],[7,1,3],[1,9,5]])
+puts find_richest_customer_wealth([[2, 8, 7], [7, 1, 3], [1, 9, 5]])
 # => 17

data_structures/arrays/shuffle_array.rb

@@ -28,8 +28,8 @@
 #
 def shuffle(nums, n)
   result = []
-  (0..n-1).count do |i|
+  (0..n - 1).count do |i|
-    result.push(nums[i], nums[i+n])
+    result.push(nums[i], nums[i + n])
   end
   result
 end
@@ -55,7 +55,7 @@ print(shuffle(nums, n))
 
 def shuffle(nums, n)
   current_index = 1
-  (0..n-1).each do |i|
+  (0..n - 1).each do |i|
     nums.insert(current_index, nums.delete_at(i + n))
     current_index += 2
   end
@@ -88,8 +88,8 @@ def shuffle(nums, n)
 
   while p1 < n
     result.push(nums[p1], nums[p2])
-    p1 +=1
+    p1 += 1
-    p2 +=1
+    p2 += 1
   end
 
   result

data_structures/arrays/single_number.rb

@@ -18,7 +18,7 @@ def single_number(nums)
   result_hash = {}
   nums.each do |num|
     if result_hash[num]
-      result_hash[num] +=1 
+      result_hash[num] += 1
     else
       result_hash[num] = 1
     end

data_structures/arrays/strings/almost_palindrome_checker.rb

@@ -28,16 +28,14 @@
 # Time Complexity: O(n)
 # Space Complexity: O(1)
 
-
 def almost_palindrome_checker(string)
   p1 = 0
   p2 = string.length - 1
   array = string.split('')
 
   while p1 < p2
-    if array[p1] != array[p2]
+    return palindrome_checker(array, p1, p2 - 1) || palindrome_checker(array, p1 + 1, p2) if array[p1] != array[p2]
-      return palindrome_checker(array, p1, p2 - 1) || palindrome_checker(array, p1 + 1, p2)
+
-    end
     p1 += 1
     p2 -= 1
   end
@@ -47,9 +45,8 @@ end
 
 def palindrome_checker(array, p1, p2)
   while p1 < p2
-    if array[p1] != array[p2]
+    return false if array[p1] != array[p2]
-      return false
+
-    end
     p1 += 1
     p2 -= 1
   end

data_structures/arrays/strings/jewels_and_stones.rb

@@ -36,17 +36,15 @@ def find_jewels(jewels, stones)
   result = 0
   jewels_array.each do |jewel|
     stones_array.each do |stone|
-      if jewel == stone
+      result += 1 if jewel == stone
-        result += 1
-      end
     end
   end
   result
 end
 
-puts find_jewels("aA", "aAAbbbb")
+puts find_jewels('aA', 'aAAbbbb')
 # => 3
-puts find_jewels("z", "ZZ")
+puts find_jewels('z', 'ZZ')
 # => 0
 
 #
@@ -80,7 +78,7 @@ def find_jewels(jewels, stones)
   result
 end
 
-puts find_jewels("aA", "aAAbbbb")
+puts find_jewels('aA', 'aAAbbbb')
 # => 3
-puts find_jewels("z", "ZZ")
+puts find_jewels('z', 'ZZ')
 # => 0

data_structures/arrays/strings/remove_vowels.rb

@@ -26,9 +26,7 @@ def remove_vowels(s)
   start_array = s.split('')
 
   start_array.each do |letter|
-    if letter != 'a' && letter != 'e' && letter != 'i' && letter != 'o' && letter != 'u'
+    result_array.push(letter) if letter != 'a' && letter != 'e' && letter != 'i' && letter != 'o' && letter != 'u'
-      result_array.push(letter)
-    end
   end
 
   result_array.join('')

data_structures/arrays/sudoku.rb

@@ -20,7 +20,8 @@ def is_valid_sudoku(board)
   board.each do |row|
     row_hash = Hash.new(0)
     row.each do |num|
-      next if num == "."
+      next if num == '.'
+
       row_hash[num] += 1
     end
     rows << row_hash
@@ -28,10 +29,8 @@ def is_valid_sudoku(board)
 
   # check each row hash for duplicated value
   rows.each do |row|
-    row.each do |k, v|
+    row.each do |_k, v|
-      if v > 1
+      return false if v > 1
-        return false
-      end
     end
   end
 
@@ -39,7 +38,8 @@ def is_valid_sudoku(board)
   (0..8).each do |i|
     column_hash = Hash.new(0)
     board.each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       column_hash[row[i]] += 1
       columns << column_hash
     end
@@ -47,10 +47,8 @@ def is_valid_sudoku(board)
 
   # check each column hash for duplicated value
   columns.each do |column|
-    column.each do |k, v|
+    column.each do |_k, v|
-      if v > 1
+      return false if v > 1
-        return false
-      end
     end
   end
 
@@ -58,17 +56,20 @@ def is_valid_sudoku(board)
   (0..2).each do |i|
     grid_hash = Hash.new(0)
     board.first(3).each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board[3..5].each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board.each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
@@ -76,17 +77,20 @@ def is_valid_sudoku(board)
   (3..5).each do |i|
     grid_hash = Hash.new(0)
     board.first(3).each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board[3..5].each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board.each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
@@ -94,17 +98,20 @@ def is_valid_sudoku(board)
   (6..8).last(3).each do |i|
     grid_hash = Hash.new(0)
     board.first(3).each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board[3..5].each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
     board.each do |row|
-      next if row[i] == "."
+      next if row[i] == '.'
+
       grid_hash[row[i]] += 1
       grids << grid_hash
     end
@@ -112,63 +119,61 @@ def is_valid_sudoku(board)
 
   # check each grid hash for duplicated value
   grids.each do |grid|
-    grid.each do |k, v|
+    grid.each do |_k, v|
-      if v > 1
+      return false if v > 1
-        return false
-      end
     end
   end
 
   true
 end
 
-board = [["5","3",".",".","7",".",".",".","."],
+board = [['5', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => true
 
-board = [["8","3",".",".","7",".",".",".","."],
+board = [['8', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in column
 
-board = [["8","3",".",".","7",".","3",".","."],
+board = [['8', '3', '.', '.', '7', '.', '3', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in row
 
-board = [["8","3",".",".","7",".",".",".","."],
+board = [['8', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        [".",".",".",".","6",".",".",".","3"],
+         ['.', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in 3x3 grid
@@ -181,6 +186,7 @@ require 'set'
 def is_valid_sudoku(board)
   return false unless check_rows(board)
   return false unless check_cols(board)
+
   row = -3
   while (row += 3) < 9
     col = - 3
@@ -198,8 +204,9 @@ def check_grid(board, start_point)
   ss = Set.new
   (row..(row + 2)).each do |cur_row|
     (col..(col + 2)).each do |cur_col|
-      next if board[cur_row][cur_col] == "."
+      next if board[cur_row][cur_col] == '.'
       return false if ss.member?(board[cur_row][cur_col])
+
       ss.add board[cur_row][cur_col]
     end
   end
@@ -209,8 +216,9 @@ end
 def check_col(board, col)
   ss = Set.new
   (0..8).each do |row|
-    next if board[row][col] == "."
+    next if board[row][col] == '.'
     return false if ss.member?(board[row][col])
+
     ss.add board[row][col]
   end
   true
@@ -219,8 +227,9 @@ end
 def check_row(board, row)
   ss = Set.new
   (0..8).each do |col|
-    next if board[row][col] == "."
+    next if board[row][col] == '.'
     return false if ss.member?(board[row][col])
+
     ss.add board[row][col]
   end
   true
@@ -240,53 +249,53 @@ def check_cols(board)
   true
 end
 
-board = [["5","3",".",".","7",".",".",".","."],
+board = [['5', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => true
 
-board = [["8","3",".",".","7",".",".",".","."],
+board = [['8', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in column
 
-board = [["8","3",".",".","7",".","3",".","."],
+board = [['8', '3', '.', '.', '7', '.', '3', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        ["8",".",".",".","6",".",".",".","3"],
+         ['8', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in row
 
-board = [["8","3",".",".","7",".",".",".","."],
+board = [['8', '3', '.', '.', '7', '.', '.', '.', '.'],
-        ["6",".",".","1","9","5",".",".","."],
+         ['6', '.', '.', '1', '9', '5', '.', '.', '.'],
-        [".","9","8",".",".",".",".","6","."],
+         ['.', '9', '8', '.', '.', '.', '.', '6', '.'],
-        [".",".",".",".","6",".",".",".","3"],
+         ['.', '.', '.', '.', '6', '.', '.', '.', '3'],
-        ["4",".",".","8",".","3",".",".","1"],
+         ['4', '.', '.', '8', '.', '3', '.', '.', '1'],
-        ["7",".",".",".","2",".",".",".","6"],
+         ['7', '.', '.', '.', '2', '.', '.', '.', '6'],
-        [".","6",".",".",".",".","2","8","."],
+         ['.', '6', '.', '.', '.', '.', '2', '8', '.'],
-        [".",".",".","4","1","9",".",".","5"],
+         ['.', '.', '.', '4', '1', '9', '.', '.', '5'],
-        [".",".",".",".","8",".",".","7","9"]]
+         ['.', '.', '.', '.', '8', '.', '.', '7', '9']]
 print(is_valid_sudoku(board))
 # => false
 # explanation: duplicated value in 3x3 grid

data_structures/arrays/two_sum.rb

@@ -71,9 +71,7 @@ def two_sum(nums, target)
     target_difference = target - num
 
     nums.each_with_index do |num, j|
-      if i != j && num == target_difference
+      return [i, j] if i != j && num == target_difference
-        return [i, j]
-      end
     end
   end
 end

data_structures/hash_table/anagram_checker.rb

@@ -38,7 +38,7 @@ def is_anagram(s, t)
     counter[t[i]] -= 1
   end
 
-  counter.each do |k, v|
+  counter.each do |_k, v|
     return false unless v == 0
   end
 

data_structures/hash_table/arrays_intersection.rb

@@ -32,7 +32,7 @@ def arrays_intersection(arr1, arr2, arr3)
   add_to_hash(arr2, hash)
   add_to_hash(arr3, hash)
 
-  hash.select { |key, value| value == 3 }.keys
+  hash.select { |_key, value| value == 3 }.keys
 end
 
 def add_to_hash(arr, hash)

data_structures/hash_table/common_characters.rb

@@ -44,8 +44,8 @@ def common_characters(arr)
   result
 end
 
-puts common_characters(["bella","label","roller"])
+puts common_characters(%w[bella label roller])
 # => ["e","l","l"]
 
-puts common_characters(["cool","lock","cook"])
+puts common_characters(%w[cool lock cook])
 # => ["c","o"]

data_structures/hash_table/isomorphic_strings.rb

@@ -45,20 +45,20 @@ def isomorphic_strings_check(s, t)
     else
       # return false if char2 is already mapped to a different character
       return false if set.include?(char2)
+
       # checks passed: add new character map and track that char2 has been mapped
       map[char1] = char2
       set << char2
     end
-
   end
-  return true
+  true
 end
 
-puts isomorphic_strings_check("egg", "add")
+puts isomorphic_strings_check('egg', 'add')
 # => true
 
-puts isomorphic_strings_check("foo", "bar")
+puts isomorphic_strings_check('foo', 'bar')
 # => false
 
-puts isomorphic_strings_check("paper", "title")
+puts isomorphic_strings_check('paper', 'title')
 # => true

data_structures/hash_table/richest_customer_wealth.rb

@@ -42,18 +42,16 @@ def find_richest_customer_wealth(accounts)
   end
 
   highest_value = 0
-  result_hash.each do |k, v|
+  result_hash.each do |_k, v|
-    if v > highest_value
+    highest_value = v if v > highest_value
-      highest_value = v
-    end
   end
 
   highest_value
 end
 
-puts find_richest_customer_wealth([[1,2,3],[3,2,1]])
+puts find_richest_customer_wealth([[1, 2, 3], [3, 2, 1]])
 # => 6
-puts find_richest_customer_wealth([[1,5],[7,3],[3,5]])
+puts find_richest_customer_wealth([[1, 5], [7, 3], [3, 5]])
 # => 10
-puts find_richest_customer_wealth([[2,8,7],[7,1,3],[1,9,5]])
+puts find_richest_customer_wealth([[2, 8, 7], [7, 1, 3], [1, 9, 5]])
 # => 17

data_structures/hash_table/two_sum.rb

@@ -48,9 +48,7 @@ def two_sum(nums, target)
   nums.each_with_index do |num, i|
     difference_target = target - num
 
-    if hash[difference_target] && hash[difference_target] != i
+    return [i, hash[difference_target]] if hash[difference_target] && hash[difference_target] != i
-      return [i, hash[difference_target]]
-    end
   end
 end
 

data_structures/hash_table/uncommon_words.rb

@@ -24,7 +24,7 @@
 # Time Complexitiy: O(n)
 
 def find_uncommon_words(strA, strB)
-  array = strA.concat(" ", strB).split(" ")
+  array = strA.concat(' ', strB).split(' ')
   hash = Hash.new(0)
   result = []
 
@@ -33,16 +33,14 @@ def find_uncommon_words(strA, strB)
   end
 
   hash.each do |k, v|
-    if v < 2
+    result.push(k) if v < 2
-      result.push(k)
-    end
   end
 
   result
 end
 
-puts find_uncommon_words("this apple is sweet", "this apple is sour")
+puts find_uncommon_words('this apple is sweet', 'this apple is sour')
 # => ["sweet", "sour"]
 
-puts find_uncommon_words("apple apple", "banana")
+puts find_uncommon_words('apple apple', 'banana')
 # => ["banana"]

data_structures/queues/circular_queue.rb

@@ -38,8 +38,7 @@ class CircularQueue
   end
 
   def add(x)
-    raise "Queue is at max capacity" if size == max_size
+    raise 'Queue is at max capacity' if size == max_size
-
 
     queue[back] = x
     @back = (back + 1) % max_size
@@ -47,7 +46,7 @@ class CircularQueue
   end
 
   def pop
-    raise "Queue is empty" if size == 0
+    raise 'Queue is empty' if size == 0
 
     temp = queue[front]
     queue[front] = nil
@@ -62,7 +61,7 @@ queue = CircularQueue.new(3)
 
 begin
   queue.pop
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 
@@ -72,7 +71,7 @@ queue.add(3)
 
 begin
   queue.add(4)
-rescue => e
+rescue StandardError => e
   puts e.message
 end
 

dynamic_programming/climbing_stairs.rb

@@ -1,47 +1,43 @@
-#You are climbing a staircase. It takes n steps to reach the top.
+# You are climbing a staircase. It takes n steps to reach the top.
-#Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
+# Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
 
-#Example 1:
+# Example 1:
-#Input: n = 2
+# Input: n = 2
-#Output: 2
+# Output: 2
-#Explanation: There are two ways to climb to the top.
+# Explanation: There are two ways to climb to the top.
-#1. 1 step + 1 step
+# 1. 1 step + 1 step
-#2. 2 steps
+# 2. 2 steps
 
-#Example 2:
+# Example 2:
-#Input: n = 3
+# Input: n = 3
-#Output: 3
+# Output: 3
-#Explanation: There are three ways to climb to the top.
+# Explanation: There are three ways to climb to the top.
-#1. 1 step + 1 step + 1 step
+# 1. 1 step + 1 step + 1 step
-#2. 1 step + 2 steps
+# 2. 1 step + 2 steps
-#3. 2 steps + 1 step
+# 3. 2 steps + 1 step
 
-#Constraints:
+# Constraints:
-#1 <= n <= 45
+# 1 <= n <= 45
 
+# Dynamic Programming, Recursive Bottom Up Approach - O(n) Time / O(n) Space
+# Init memoization hash (only 1 parameter)
+# Set base cases which are memo[0] = 1 and memo[1] = 1, since there are only 1 way to get to each stair
+# Iterate from 2..n and call recurse(n, memo) for each value n.
+# Return memo[n].
 
-
+# recurse(n, memo) - Recurrence Relation is n = (n - 1) + (n - 2)
-
+# return memo[n] if memo[n] exists.
-#Dynamic Programming, Recursive Bottom Up Approach - O(n) Time / O(n) Space
+# otherwise, memo[n] = recurse(n - 1, memo) + recurse(n - 2, memo)
-#Init memoization hash (only 1 parameter)
-#Set base cases which are memo[0] = 1 and memo[1] = 1, since there are only 1 way to get to each stair
-#Iterate from 2..n and call recurse(n, memo) for each value n. 
-#Return memo[n].
-
-#recurse(n, memo) - Recurrence Relation is n = (n - 1) + (n - 2)
-#return memo[n] if memo[n] exists. 
-#otherwise, memo[n] = recurse(n - 1, memo) + recurse(n - 2, memo)               
-
 
 # @param {Integer} n
 # @return {Integer}
 def climb_stairs(n)
-    memo = Hash.new
+  memo = {}
 
   memo[0] = 1
   memo[1] = 1
 
-    return memo[n] if n == 0 || n == 1
+  return memo[n] if [0, 1].include?(n)
 
   (2..n).each do |n|
     recurse(n, memo)
@@ -50,14 +46,12 @@ def climb_stairs(n)
   memo[n]
 end
 
-
 def recurse(n, memo)
   return memo[n] if memo[n]
 
   memo[n] = recurse(n - 1, memo) + recurse(n - 2, memo)
 end
 
-
 puts climb_stairs(2)
 # => 2
 

dynamic_programming/pascal_triangle_ii.rb

@@ -69,6 +69,7 @@ end
 
 def generate(num_rows)
   return [[1]] if num_rows < 1
+
   result = [[1], [1, 1]]
 
   (2...num_rows + 1).each do |row|

maths/abs_max.rb

@@ -3,10 +3,10 @@
 
 def abs_max(x, y)
   num = x - y
-  max_value = ((x + y + num.abs()) / 2)
+  max_value = ((x + y + num.abs) / 2)
   "The Abs Max of #{x} and #{y} is #{max_value}."
-  rescue
+rescue StandardError
-    "Error: Provide number only!"
+  'Error: Provide number only!'
 end
 
 # Valid inputs
@@ -20,11 +20,11 @@ puts abs_max(9, -121)
 # The Abs Max of 9 and -121 is 9.
 
 # Invalid inputs
-puts abs_max(2, "-1")
+puts abs_max(2, '-1')
 # Error: Provide number only!
 
-puts abs_max("3", "5")
+puts abs_max('3', '5')
 # Error: Provide number only!
 
-puts abs_max("a", "5")
+puts abs_max('a', '5')
 # Error: Provide number only!

maths/abs_min.rb

@@ -3,10 +3,10 @@
 
 def abs_min(x, y)
   num = x - y
-  min_value = ((x + y - num.abs()) / 2)
+  min_value = ((x + y - num.abs) / 2)
   "The Abs Min of #{x} and #{y} is #{min_value}."
-  rescue
+rescue StandardError
-    "Error: Provide number only!"
+  'Error: Provide number only!'
 end
 
 #
@@ -24,11 +24,11 @@ puts abs_min(9, -121)
 #
 # Invalid inputs
 #
-puts abs_min(2, "-1")
+puts abs_min(2, '-1')
 # Error: Provide number only!
 
-puts abs_min("3", "5")
+puts abs_min('3', '5')
 # Error: Provide number only!
 
-puts abs_min("a", "5")
+puts abs_min('a', '5')
 # Error: Provide number only!

maths/add.rb

@@ -4,10 +4,10 @@
 
 def add(*array)
   sum = 0
-  array.each { |a| sum+=a }
+  array.each { |a| sum += a }
   puts "The sum of following elements #{array} is #{sum}"
-  rescue
+rescue StandardError
-    puts "Error: Please provide number only!"
+  puts 'Error: Please provide number only!'
 end
 
 #
@@ -27,8 +27,8 @@ puts add(25, 45)
 # Invalid inputs
 #
 
-puts add("1", 2, 3)
+puts add('1', 2, 3)
 # Error: Please provide number only!
 
-puts add("a", 1)
+puts add('a', 1)
 # Error: Please provide number only!

maths/armstrong_number.rb

@@ -11,9 +11,9 @@ def armstrong_number(number)
   num = number
   sum = 0
   len = number.digits.count
-  while(number != 0)
+  while number != 0
     remainder = number % 10
-    sum += remainder ** len
+    sum += remainder**len
     number /= 10
   end
 
@@ -22,8 +22,8 @@ def armstrong_number(number)
   else
     "The number #{num} is not an Armstrong number."
   end
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 #
@@ -50,8 +50,8 @@ puts armstrong_number(123)
 #
 # Invalid inputs
 #
-puts armstrong_number("153")
+puts armstrong_number('153')
 # Error: Please provide number only!
 
-puts armstrong_number("a")
+puts armstrong_number('a')
 # Error: Please provide number only!

maths/average_mean.rb

@@ -5,15 +5,15 @@ module AverageMean
   def self.average_mean(n, *array)
     if n.instance_of? Integer
       if n == array.size
-        puts "The average mean of the following elements #{array} is #{array.sum/array.size}."
+        puts "The average mean of the following elements #{array} is #{array.sum / array.size}."
       else
         puts "Provide the required #{n} elements properly!"
       end
     else
       raise
     end
-    rescue
+  rescue StandardError
-      puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 end
 
@@ -24,5 +24,5 @@ AverageMean.average_mean(3, 2, 2, 2)
 
 # Invalid inputs
 AverageMean.average_mean(2, 3, 1, 5)
-AverageMean.average_mean(2, 3, "a")
+AverageMean.average_mean(2, 3, 'a')
-AverageMean.average_mean("a", 1, 2)
+AverageMean.average_mean('a', 1, 2)

maths/average_median.rb

@@ -6,8 +6,8 @@ module AverageMedian
     if n.instance_of? Integer
       if n == array.size
         array.sort
-        if array.size % 2 == 0
+        if array.size.even?
-          mid_element_1 = array.size/2
+          mid_element_1 = array.size / 2
           mid_element_2 = mid_element_1 + 1
           puts "The average median of the following elements #{array} is #{(array[mid_element_1 - 1] + array[mid_element_2 - 1]) / 2}."
         else
@@ -20,8 +20,8 @@ module AverageMedian
     else
       raise
     end
-    rescue
+  rescue StandardError
-      puts "Error: Please provide number only!"
+    puts 'Error: Please provide number only!'
   end
 end
 
@@ -48,7 +48,7 @@ puts AverageMedian.average_median(1, 5)
 puts AverageMedian.average_median(2, 3, 1, 5)
 # Provide the required 2 elements properly!
 
-puts AverageMedian.average_median(2, 3, "a")
+puts AverageMedian.average_median(2, 3, 'a')
 # Traceback (most recent call last):
 #         4: from /Users/voliveira/.rvm/rubies/ruby-2.7.0/bin/irb:23:in `<main>'
 #         3: from /Users/voliveira/.rvm/rubies/ruby-2.7.0/bin/irb:23:in `load'
@@ -56,5 +56,5 @@ puts AverageMedian.average_median(2, 3, "a")
 #         1: from (irb):30
 # NameError (undefined local variable or method `verageMedian' for main:Object)
 
-puts AverageMedian.average_median("a", 1, 2)
+puts AverageMedian.average_median('a', 1, 2)
 # Error: Please provide number only!

maths/count_sorted_vowel_strings.rb

@@ -26,7 +26,6 @@
 # Input: n = 33
 # Output: 66045
 
-
 #
 # Approach: Math
 #

maths/factorial.rb

@@ -1,8 +1,6 @@
-=begin
+# A ruby program calculate factorial of a given number.
-A ruby program calculate factorial of a given number.
+# Mathematical Explanation: The factorial of a number is the product of all the integers from 1 to that number.
-Mathematical Explanation: The factorial of a number is the product of all the integers from 1 to that number. 
+# i.e: n! = n*(n-1)*(n-2)......*2*1
-i.e: n! = n*(n-1)*(n-2)......*2*1
-=end
 
 #
 # Approach: Interative

maths/factorial_non_recursive_non_iterative.rb

@@ -8,15 +8,15 @@
 
 def factorial(number)
   if number < 0
-    "Please check your input number! The given number is a negative number."
+    'Please check your input number! The given number is a negative number.'
   elsif number == 0
     "The factorial of #{number} is 1."
   else
     result = (1..number).inject(:*)
     "The factorial of #{number} is #{result}."
   end
-  rescue
+rescue StandardError
-    "Error: Please provide integer only!"
+  'Error: Please provide integer only!'
 end
 
 # Valid inputs
@@ -36,8 +36,8 @@ puts factorial(-5)
 # Please check your input number! The given number is a negative number.
 
 # Invalid inputs
-puts factorial("a")
+puts factorial('a')
 # Error: Please provide integer only!
 
-puts factorial("2")
+puts factorial('2')
 # Error: Please provide integer only!

maths/find_max.rb

@@ -4,27 +4,25 @@
 def find_max(*array)
   max = array[0]
   array.each do |a|
-    if a >= max
+    max = a if a >= max
-      max = a
-    end
   end
   "The Max of the following elements #{array} is #{max}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Max method will return the maximum element from the set of input elements provided
 def predefined_max(*array)
   "The Max of the following elements #{array} is #{array.max}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Sort method will sort the elements in ascending order. Last method will return the end element out of the array
 def predefined_sort_last_max(*array)
-  "The Max of the following elements #{array} is #{array.sort.last}."
+  "The Max of the following elements #{array} is #{array.max}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Using find_max
@@ -36,7 +34,7 @@ puts find_max(-221, -852, -1100, -10)
 # The Max of the following elements [-221, -852, -1100, -10] is -10.
 
 # Invalid inputs
-puts find_max(5, "95", 2)
+puts find_max(5, '95', 2)
 # Error: Please provide number only!
 
 # Using predefined_max
@@ -48,7 +46,7 @@ puts predefined_max(-11, -51, -10, -10)
 # The Max of the following elements [-11, -51, -10, -10] is -10.
 
 # Invalid inputs
-puts predefined_max("x", 5, 95, 2)
+puts predefined_max('x', 5, 95, 2)
 # Error: Please provide number only!
 
 # Using predefined_sort_last_max
@@ -60,5 +58,5 @@ puts predefined_sort_last_max(-21, -52, -100, -1)
 # The Max of the following elements [-21, -52, -100, -1] is -1.
 
 # Invalid inputs
-puts predefined_sort_last_max(5, 95, 2, "a")
+puts predefined_sort_last_max(5, 95, 2, 'a')
 # Error: Please provide number only!

maths/find_min.rb

@@ -4,27 +4,25 @@
 def find_min(*array)
   min = array[0]
   array.each do |a|
-    if a <= min
+    min = a if a <= min
-      min = a
-    end
   end
   "The Min of the following elements #{array} is #{min}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Min method will return the minimum element from the set of input elements provided
 def predefined_min(*array)
   "The Min of the following elements #{array} is #{array.min}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Sort method will sort the elements in ascending order. First method will return the beginning element out of the array
 def predefined_sort_first_min(*array)
-  "The Min of the following elements #{array} is #{array.sort.first}."
+  "The Min of the following elements #{array} is #{array.min}."
-  rescue
+rescue StandardError
-    "Error: Please provide number only!"
+  'Error: Please provide number only!'
 end
 
 # Using find_min
@@ -36,7 +34,7 @@ puts find_min(-221, -852, -1100, -10)
 # The Min of the following elements [-221, -852, -1100, -10] is -10.
 
 # Invalid inputs
-puts find_min(5, "95", 2)
+puts find_min(5, '95', 2)
 # Error: Please provide number only!
 
 # Using predefined_min
@@ -48,7 +46,7 @@ puts predefined_min(-11, -51, -10, -10)
 # The Min of the following elements [-11, -51, -10, -10] is -10.
 
 # Invalid inputs
-puts predefined_min("x", 5, 95, 2)
+puts predefined_min('x', 5, 95, 2)
 # Error: Please provide number only!
 
 # Using predefined_sort_first_min
@@ -60,5 +58,5 @@ puts predefined_sort_first_min(-21, -52, -100, -1)
 # The Min of the following elements [-21, -52, -100, -1] is -1.
 
 # Invalid inputs
-puts predefined_sort_first_min(5, 95, 2, "a")
+puts predefined_sort_first_min(5, 95, 2, 'a')
 # Error: Please provide number only!

maths/lucas_series.rb

@@ -13,9 +13,9 @@
 
 def lucas(number)
   golden_ratio = (1 + 5**0.5) / 2
-  ((golden_ratio**number).round()).to_i
+  (golden_ratio**number).round.to_i
-  rescue
+rescue StandardError
-    "Error: Provide number only!"
+  'Error: Provide number only!'
 end
 
 puts lucas(4)
@@ -24,7 +24,7 @@ puts lucas(4)
 puts lucas(3)
 # 4
 
-puts lucas("3")
+puts lucas('3')
 # Error: Provide number only!
 
 puts lucas(2)

maths/pascal_triangle_ii.rb

@@ -21,7 +21,7 @@
 # Space complexity: O(k).
 
 def get_row(row_index)
-  (0..row_index).map {|num| combination(row_index, num) }
+  (0..row_index).map { |num| combination(row_index, num) }
 end
 
 def combination(num1, num2)

maths/power_of_two.rb

@@ -38,7 +38,7 @@
 def is_power_of_two(n)
   if n == 1
     true
-  elsif n % 2 == 0
+  elsif n.even?
     is_power_of_two(n / 2)
   else
     false
@@ -67,9 +67,7 @@ puts is_power_of_two(n)
 # Time Complexity: O(n)
 #
 def is_power_of_two(n)
-  while n % 2 == 0 && n != 0
+  n /= 2 while n.even? && n != 0
-    n /= 2
-  end
   n == 1
 end
 

maths/prime_number.rb

@@ -3,14 +3,14 @@
 
 # Prime number check function
 def prime_number(number)
-  if number <= 1
+  non_prime_flag = if number <= 1
-    non_prime_flag = true
+                     true
                    elsif number == 2
-    non_prime_flag = false
+                     false
-  elsif number % 2 == 0
+                   elsif number.even?
-    non_prime_flag = true
+                     true
                    else
-    non_prime_flag = (2..Math.sqrt(number)).any? { |i| number % i == 0 }
+                     (2..Math.sqrt(number)).any? { |i| number % i == 0 }
                    end
 
   if !non_prime_flag

maths/roman_to_integer.rb

@@ -36,13 +36,13 @@
 # Because only a constant number of single-value variables are used, the space complexity is O(1).
 
 ROM_NUMS = {
-  "I" => 1,
+  'I' => 1,
-  "V" => 5,
+  'V' => 5,
-  "X" => 10,
+  'X' => 10,
-  "L" => 50,
+  'L' => 50,
-  "C" => 100,
+  'C' => 100,
-  "D" => 500,
+  'D' => 500,
-  "M" => 1000
+  'M' => 1000
 }
 
 # Now, recall that each symbol adds its own value, except for when a smaller
@@ -61,7 +61,7 @@ def roman_to_int(s)
 
   s.chars.each_with_index do |el, i|
     # subtractive case: if at least 2 symbols remaining AND value of s[i] < value of s[i + 1]
-    if ROM_NUMS[s[i + 1]] && ROM_NUMS[el] < ROM_NUMS[s[i+1]]
+    if ROM_NUMS[s[i + 1]] && ROM_NUMS[el] < ROM_NUMS[s[i + 1]]
       temp = ROM_NUMS[el]
     else
       # Else this is NOT the subtractive case.
@@ -73,24 +73,24 @@ def roman_to_int(s)
   res
 end
 
-s = "III"
+s = 'III'
 puts roman_to_int(s)
 # Output: 3
 
-s = "IV"
+s = 'IV'
 puts roman_to_int(s)
 # Output: 4
 
-s = "IX"
+s = 'IX'
 puts roman_to_int(s)
 # Output: 9
 
-s = "LVIII"
+s = 'LVIII'
 puts roman_to_int(s)
 # Output: 58
 # Explanation: L = 50, V= 5, III = 3.
 
-s = "MCMXCIV"
+s = 'MCMXCIV'
 puts roman_to_int(s)
 # Output: 1994
 # Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

other/number_of_days.rb

@@ -13,7 +13,6 @@
 #
 # Constraints: The given dates are valid dates between the years 1971 and 2100.
 
-
 #
 # Approach 1: Using Ruby built-in feature Date.parse
 # Time complexity: O(1)
@@ -28,8 +27,8 @@ def number_of_days(date1, date2)
   (end_date - beginning_date).to_i.abs
 end
 
-puts number_of_days("2019-06-29", "2019-06-30")
+puts number_of_days('2019-06-29', '2019-06-30')
 # => 1
 
-puts number_of_days("2020-01-15", "2019-12-31")
+puts number_of_days('2020-01-15', '2019-12-31')
 # => 15

searches/number_of_islands.rb

@@ -1,79 +1,76 @@
-#Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
+# Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
-#An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
+# An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
 
-#Example 1:
+# Example 1:
-#Input: grid = [
+# Input: grid = [
 #  ["1","1","1","1","0"],
 #  ["1","1","0","1","0"],
 #  ["1","1","0","0","0"],
 #  ["0","0","0","0","0"]
-#]
+# ]
-#Output: 1
+# Output: 1
 
-#Example 2:
+# Example 2:
-#Input: grid = [
+# Input: grid = [
 #  ["1","1","0","0","0"],
 #  ["1","1","0","0","0"],
 #  ["0","0","1","0","0"],
 #  ["0","0","0","1","1"]
-#]
+# ]
-#Output: 3
+# Output: 3
 
-#Constraints:
+# Constraints:
-#m == grid.length
+# m == grid.length
-#n == grid[i].length
+# n == grid[i].length
-#1 <= m, n <= 300
+# 1 <= m, n <= 300
-#grid[i][j] is '0' or '1'.
+# grid[i][j] is '0' or '1'.
 
+# DFS, Recursive Bottom Up Approach - O(n*m) Time / O(1) Space
+# Init num_of_islands = 0, return if the grid is empty
+# Start a double loop with index to iterate through each plot (each value is a plot of either water or land in this case)
+# if the plot is land, dfs(grid, x, y)
+# num_of_islands += 1
+# Return num_of_islands
 
-
+# dfs(grid, x, y)
-
+# Return if x or y are out of bounds, or if the plot is water
-#DFS, Recursive Bottom Up Approach - O(n*m) Time / O(1) Space
+# Make the current plot water
-#Init num_of_islands = 0, return if the grid is empty
+# Call dfs again for up, down, left, and right
-#Start a double loop with index to iterate through each plot (each value is a plot of either water or land in this case)
-#if the plot is land, dfs(grid, x, y)
-#num_of_islands += 1
-#Return num_of_islands
-
-#dfs(grid, x, y)
-#Return if x or y are out of bounds, or if the plot is water
-#Make the current plot water
-#Call dfs again for up, down, left, and right     
 
 # @param {Character[][]} grid
 # @return {Integer}
 def num_islands(grid)
   return 0 if grid.empty?
 
-    #init num of islands
+  # init num of islands
   islands = 0
 
-    #loop through each element (plot) in the 2d array
+  # loop through each element (plot) in the 2d array
   grid.each_with_index do |row, x|
     row.each_with_index do |plot, y|
-        #if the plot is water, start a dfs
+      # if the plot is water, start a dfs
-        if plot == "1"
+      next unless plot == '1'
+
       dfs(grid, x, y)
-          #add 1 to islands once all connected land plots are searched
+      # add 1 to islands once all connected land plots are searched
       islands += 1
     end
   end
-    end
 
-    #return ans
+  # return ans
   islands
 end
 
 def dfs(grid, x, y)
-    #don't search if out of bounds, or if it's already water
+  # don't search if out of bounds, or if it's already water
-    return if x < 0 || x >= grid.length || y < 0 || y >= grid[0].length || grid[x][y] == "0"
+  return if x < 0 || x >= grid.length || y < 0 || y >= grid[0].length || grid[x][y] == '0'
 
-    #set the plot to water
+  # set the plot to water
-    grid[x][y] = "0"
+  grid[x][y] = '0'
 
-    #search each adjacent plot
+  # search each adjacent plot
-    dfs(grid, x - 1, y) #up
+  dfs(grid, x - 1, y) # up
-    dfs(grid, x + 1, y) #down
+  dfs(grid, x + 1, y) # down
-    dfs(grid, x, y - 1) #left
+  dfs(grid, x, y - 1) # left
-    dfs(grid, x, y + 1) #right
+  dfs(grid, x, y + 1) # right
 end

sorting/cocktail_sort.rb

@@ -11,7 +11,10 @@ def cocktail_sort(array)
       end
     end
     break unless swapped
-    start, finish, way = swapped, start, -way
+
+    finish = start
+    start = swapped
+    way = -way
   end
   array
 end

sorting/cocktail_sort_test.rb

@@ -9,4 +9,3 @@ class TestInsertionSort < Minitest::Test
     cocktail_sort(input)
   end
 end
-

sorting/comb_sort.rb

@@ -1,7 +1,7 @@
 def comb_sort(array)
   gap = array.length
   swaps = true
-  while gap > 1 or swaps
+  while (gap > 1) || swaps
     gap = [1, (gap / 1.25).to_i].max
     swaps = false
     0.upto(array.length - gap - 1) do |i|

sorting/pancake_sort.rb

@@ -1,5 +1,6 @@
 def pancake_sort(array)
   return array if array.length <= 1
+
   (array.length - 1).downto(1) do |index|
     max_index = array[0..index].index(array[0..index].max)
     next if max_index == index