exercism-68 Run Length Encoding

Author: kumar91gopi

README.md

@@ -285,6 +285,7 @@ solution of many challenges of [Leetcode](https://leetcode.com/), [Exercism](htt
 65. [Matching Brackets](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/matching_brackets.rb)
 66. [All Your Base](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/all_your_base.rb)
 67. [Allergies](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/allergies.rb)
+68. [Run Length Encoding](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/run_length_encoding.rb)
 
 <a name="leetcode"/>
 

exercism/run_length_encoding.rb

@@ -0,0 +1,65 @@
+# Problem: https://exercism.org/tracks/ruby/exercises/run-length-encoding
+
+# Solution (Brute force)
+class RunLengthEncoding
+    def self.encode(input)
+      return "" if input==""
+      encoded_msg = ""
+      curr_char_count = 0
+      prev_char = ""
+      input.chars.each do |char|
+        if prev_char != char
+          encoded_msg+="#{curr_char_count>1?curr_char_count:""}#{prev_char}"
+          prev_char = char
+          curr_char_count=0
+        end
+        curr_char_count+=1
+      end
+      encoded_msg+="#{curr_char_count>1?curr_char_count:""}#{prev_char}"
+      encoded_msg
+    end
+
+    def self.decode(encoded_input)
+      decoded_msg = ""
+      curr_num_str = ""
+      curr_char = ""
+      encoded_input.chars.each do |char|
+        if char.match(/\d/)
+          curr_num_str+=char
+          next
+        end
+        decoded_msg+="#{curr_num_str=="" ? char: (char*curr_num_str.to_i)}"
+        curr_num_str = ""
+      end
+      decoded_msg     
+    end
+end
+
+# Solution(Using Regex)
+class RunLengthEncoding
+    def self.encode(input)
+      input.gsub(/(.)\1+/) { |m| "#{m.length}#{m[0]}" }
+    end
+
+    def self.decode(input)
+      input.gsub(/\d+./) { |m| m[-1] * m.to_i }
+    end
+end
+
+# Solution(Using Collections)
+class RunLengthEncoding
+    def self.encode(input)
+      input
+        .chars
+        .chunk { |c| c }
+        .collect { |k,v| [v.length > 1 ? v.length : '', k].join }
+        .join
+    end
+
+    def self.decode(input)
+      input
+        .scan(/(\d*)([ \w]+?)/)
+        .map { |c| c[1] * (c[0] != '' ? c[0].to_i : 1) }
+        .join
+    end
+end