C++ Vigenere Cipher

Given the function shiftAlphaCharacter(char c, int n), which accepts char c and shifts c by n times. Ex: ('a', 3) outputs d.

Write the implementations of function string vigenereCipher(string original, string keyword), which encrypts the original string by shifting every alphabetical character of the string using keywod. Call shiftAlphaCharacter().

The keywod can only consist of uppercase alphabets, A is 0, B is 1, ... Z is 25.

Ex:

vigenereCipher("Meet me at the Diag at 11 p.m.", "SQUIRREL") will output "Euyb dv ee lxy Lzrk ll 11 f.g."

plaintext: Meet me at the Diag at 11 p.m. key SQUI RR EL SQU IRRE LS Q U ciphertext: Euyb dv ee lxy Lzrk 11 11 f.g