digital-cypher-vol-2

Digital cypher vol 2

Introduction

Digital Cypher assigns to each letter of the alphabet unique number. For example:

 a  b  c  d  e  f  g  h  i  j  k  l  m
 1  2  3  4  5  6  7  8  9 10 11 12 13
 n  o  p  q  r  s  t  u  v  w  x  y  z
14 15 16 17 18 19 20 21 22 23 24 25 26

Instead of letters in encrypted word we write the corresponding number, e.g. The word scout:

 s  c  o  u  t
19  3 15 21 20

Then we add to each obtained digit consecutive digits from the key. For example. In case of key equal to 1939 :

   s  c  o  u  t
  19  3 15 21 20
 + 1  9  3  9  1
 ---------------
  20 12 18 30 21
  
   m  a  s  t  e  r  p  i  e  c  e
  13  1 19 20  5 18 16  9  5  3  5
+  1  9  3  9  1  9  3  9  1  9  3
  --------------------------------
  14 10 22 29  6 27 19 18  6  12 8

Task

Write a function that accepts an array of integers code and a key number. As the result, it should return string containing a decoded message from the code.

Input / Output

The code is an array of positive integers.
The key input is a non-negative integer.

Example

decode([ 20, 12, 18, 30, 21],1939);  ==> "scout"
decode([ 14, 10, 22, 29, 6, 27, 19, 18, 6, 12, 8],1939);  ==>  "masterpiece"