Merge pull request #90 from TheAlgorithms/add-recursive-decimal-to-binary-approach

Recursive method to convert decimal to binary

DIRECTORY.md

@@ -37,7 +37,7 @@
   * [Binary To Decimal](https://github.com/TheAlgorithms/Ruby/blob/master/maths/binary_to_decimal.rb)
   * [Ceil](https://github.com/TheAlgorithms/Ruby/blob/master/maths/ceil.rb)
   * [Ceil Test](https://github.com/TheAlgorithms/Ruby/blob/master/maths/ceil_test.rb)
-  * [Iterative Decimal To Binary](https://github.com/TheAlgorithms/Ruby/blob/master/maths/iterative_decimal_to_binary.rb)
+  * [Decimal To Binary](https://github.com/TheAlgorithms/Ruby/blob/master/maths/decimal_to_binary.rb)
   * [Number Of Digits](https://github.com/TheAlgorithms/Ruby/blob/master/maths/number_of_digits.rb)
   * [Square Root](https://github.com/TheAlgorithms/Ruby/blob/master/maths/square_root.rb)
   * [Square Root Test](https://github.com/TheAlgorithms/Ruby/blob/master/maths/square_root_test.rb)

maths/decimal_to_binary.rb

@@ -0,0 +1,49 @@
+# Convert a given decimal number into binary.
+
+#
+# Approach 1: Iterative
+#
+
+def decimal_to_binary(n)
+  bin = []
+
+  until n.zero?
+    bin << n % 2
+    n /= 2
+  end
+
+  bin.reverse.join
+end
+
+puts 'Binary value of 4 is ' + decimal_to_binary(4).to_s
+# Binary value of 4 is 100
+
+puts 'Binary value of 31 is ' + decimal_to_binary(31).to_s
+# Binary value of 31 is 11111
+
+puts 'Binary value of 64 is ' + decimal_to_binary(64).to_s
+# Binary value of 64 is 1000000
+
+#
+# Approach 2: Recursive
+#
+
+def decimal_to_binary(d)
+  binary = (d % 2).to_s
+
+  return binary if d == 0
+  return 1.to_s if d == 1
+
+  binary = decimal_to_binary(d / 2).to_s + binary
+
+  binary
+end
+
+puts 'Binary value of 4 is ' + decimal_to_binary(4).to_s
+# Binary value of 4 is 100
+
+puts 'Binary value of 31 is ' + decimal_to_binary(31).to_s
+# Binary value of 31 is 11111
+
+puts 'Binary value of 64 is ' + decimal_to_binary(64).to_s
+# Binary value of 64 is 1000000

maths/iterative_decimal_to_binary.rb

@@ -1,17 +0,0 @@
-# Iterative method to convert a given decimal number into binary.
-
-def decimal_to_binary(n)
-  bin = []  
-  until n.zero?
-    bin << n % 2
-    n = n / 2
-  end
-  bin.reverse.join
-end
-
-puts 'Binary value of 4 is ' + decimal_to_binary(4).to_s
-# Binary value of 4 is 100
-puts 'Binary value of 31 is ' + decimal_to_binary(31).to_s
-# Binary value of 31 is 11111
-puts 'Binary value of 64 is ' + decimal_to_binary(64).to_s
-# Binary value of 64 is 1000000