Function decrypt

Ciphers/AffineCipher.js:91–104

* Decrypt a Affine Cipher * @param {String} str - String to be decrypted * @param {Number} a - A coefficient * @param {Number} b - B coefficient * @return {String} result - Decrypted string

(str, a, b)

 * @return {String} result - Decrypted string
 */
function decrypt(str, a, b) {
  let result = ''
  if (isCorrectFormat(str, a, b)) {
    str = str.split(' ')
    for (let x = 0; x < str.length; x++) {
      if (str[x] === '-1') result += ' '
      else {
        const charIndex = findCharIndex(str[x])
        result += key[mod(inverseMod(a, 26) * (charIndex - b), 26)]
      }
    }
    return result
  }
}
export { encrypt, decrypt }