exercism 75- Crypto Square

Author: kumar91gopi

README.md

@@ -296,7 +296,7 @@ solution of many challenges of [Leetcode](https://leetcode.com/), [Exercism](htt
 72. [Wordy](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/wordy.rb)
 73. [Secret Handshake](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/secret_handshake.rb)
 74. [Atbash Cipher](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/atbash_cipher.rb)
-
+75. [Crypto Square](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/crypto_square.rb)
 
 <a name="leetcode"/>
 

exercism/crypto_square.rb

@@ -0,0 +1,42 @@
+# Problem: https://exercism.org/tracks/ruby/exercises/crypto-square
+
+# Solution
+class Crypto
+    def initialize(plaintext)
+      @plaintext = plaintext
+    end
+
+    def ciphertext
+      normalized_text = @plaintext.downcase.gsub(/\W/,"")
+      text_len = normalized_text.length
+      return "" if text_len==0
+      col_len = Math.sqrt(text_len).ceil
+      row_len = col_len*(col_len-1) < text_len ? col_len : col_len-1
+      char_deficit = (col_len*row_len)-text_len
+      normalized_text+=(" "*char_deficit)
+      normalized_text
+          .chars
+          .each_slice(col_len)
+          .to_a
+          .transpose
+          .map{|col| col.join("")}
+          .join(" ")
+    end
+end
+
+# Solution (idiomatic)
+class Crypto
+    def initialize(plaintext)
+      @plaintext = plaintext
+    end
+    
+    def ciphertext
+      normalized_text = @plaintext.downcase.gsub(/[^\da-z]/, '')
+      length = normalized_text.length
+      return '' if length.zero?
+      cols = Math.sqrt(length).ceil
+      rows = length.quo(cols).ceil
+      rectangle_base = normalized_text + ' ' * (cols * rows - length)
+      rectangle_base.chars.each_slice(cols).to_a.transpose.map(&:join).join(' ')
+    end
+end