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  1. #include <iostream>
  2. #include <string>
  3. #include <cctype>
  4. using namespace std;
  5.  
  6. string vigenere(string text, string key, bool decrypt = false) {
  7.     string result = "";
  8.     int j = 0;
  9.     int dir = decrypt ? -1 : 1;
  10.  
  11.     // Make key uppercase
  12.     for (char &c : key) c = toupper(c);
  13.  
  14.     for (char c : text) {
  15.         if (isalpha(c)) {
  16.             char base = isupper(c) ? 'A' : 'a';
  17.             int shift = key[j % key.size()] - 'A';
  18.             result += (c - base + dir * shift + 26) % 26 + base;
  19.             j++;
  20.         } else {
  21.             result += c;
  22.         }
  23.     }
  24.  
  25.     return result;
  26. }
  27.  
  28. int main() {
  29.     string key, msg;
  30.  
  31.     cout << "Enter key: ";
  32.     cin >> key;
  33.     cin.ignore();
  34.  
  35.     cout << "Enter message: ";
  36.     getline(cin, msg);
  37.  
  38.     string enc = vigenere(msg, key);
  39.     string dec = vigenere(enc, key, true);
  40.  
  41.     cout << "Encrypted: " << enc << endl;
  42.     cout << "Decrypted: " << dec << endl;
  43.  
  44.     return 0;
  45. }
  46.  
Success #stdin #stdout 0s 5284KB
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stdin
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Standard input is empty
stdout
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Enter key: Enter message: Encrypted: 
Decrypted:
https://ideone.com/d235RL
language:
C++ (gcc 8.3)
created:
4 days ago
visibility:
public

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