decrypt message -

DecrypMessage_Cpluslpus.cpp

#include <iostream>
#include <string>

using namespace std;
/*
z .....
122
123
97

encryption

r    -> n
114

114 + 100 = 214

214 - n * 26 = range a - z , a - 97 - 97 + 26

114 + 100 - n * 26 = 110 
?

y + 100 - n * 26 = 110 
     ? 
     ? sum of source arr[i] + 1
     
y = 110 - item2No + n * 26 -> a - z
110 - 100 = 10 + 26 * 4 = 114;
111 - (114 + 100) = -103 + 8 * 26 = 105;


     step 2 
 step 1 -> 
 99    114                105                 109              101
 100   1 + 99 +114     1 + 99 + 114 + 105
how to solve the value y? 


decrption:
n -> r

110 -> 114
(char)(x)
(int)c
97 + 'c' - 'a'

*/
string decrypt( const string& word ) 
{
  // your code goes here
  int n = (int)word.size();
  
  if (n < 1)
    return "";
  
  int itemTwoNum = (int)word[0];
  
  string result;
  
  result += (char)(itemTwoNum - 1);
  
  for (int i = 1; i < n; i++) {
    int diff = (int)word[i] - itemTwoNum;
    while (diff < 97) {
      diff += 26;
    }
    
    result += (char)diff;
    
    itemTwoNum += diff;
  }
  
  return result;
}

int main() {
  return 0;
}