Merge pull request #162 from jsca-kwok/jk-palindrome

Add almost palindrome algorithm

DIRECTORY.md

@@ -36,6 +36,7 @@
     * [Sort Squares Of An Array](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/sort_squares_of_an_array.rb)
     * [Sorted Arrays Intersection](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/sorted_arrays_intersection.rb)
     * Strings
+      * [Almost Palindrome Checker](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/strings/almost_palindrome_checker.rb)
       * [Anagram Checker](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/strings/anagram_checker.rb)
       * [Jewels And Stones](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/strings/jewels_and_stones.rb)
       * [Palindrome](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/strings/palindrome.rb)

data_structures/arrays/strings/almost_palindrome_checker.rb

@@ -0,0 +1,67 @@
+# Challenge name: Almost Palindrome
+#
+# Given a string s, return true if the s can be palindrome after deleting at most one character from it.
+#
+# Example 1:
+# Input: s = "aba"
+# Output: true
+#
+# Example 2:
+# Input: s = "abca"
+# Output: true
+# Explanation: You could delete the character 'c'.
+#
+# Example 3:
+# Input: s = "abc"
+# Output: false
+#
+# Constraints:
+# 1 <= s.length <= 105
+# s consists of lowercase English letters.
+
+#
+# Approach 1: Two Pointers
+#
+
+# Complexity Analysis:
+#
+# 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)
+    end
+    p1 += 1
+    p2 -= 1
+  end
+
+  true
+end
+
+def palindrome_checker(array, p1, p2)
+  while p1 < p2
+    if array[p1] != array[p2]
+      return false
+    end
+    p1 += 1
+    p2 -= 1
+  end
+
+  true
+end
+
+puts almost_palindrome_checker('aba')
+# => true
+
+puts almost_palindrome_checker('abca')
+# => true
+
+puts almost_palindrome_checker('abc')
+# => false