Shift string Code Challenge

ShiftStrings.cpp

using namespace std;

string caesarCypherEncryptor(string str, int key) {
  for (int i = 0; i < str.size(); i++) {
		int charCode = (int)str[i];
		int nextCode = charCode + (key % 26); // Protect from max alphabet
		int modus = (nextCode % 'z') + 'a' - 1; // Protect from max Z, and min A
		// Add min in this case, a.
		int resultCode = nextCode > 'z' ? modus : nextCode; 
		str[i] = (char)resultCode;
	}
  return str;
}