7.s.2

#include <iostream>
#include <string>
using namespace std;

char getCaesar(string* alphabet, char in, int shift) {
    bool isUpper = isupper(in);
    if (isUpper)// to lower case
        in += 32;
    int lenght = alphabet->length(), resindex;
    if (shift > lenght)
        shift %= lenght;
    resindex = alphabet->find(in, 0);
    if (resindex < 0)
        return '_';
    resindex += shift;
    resindex %= lenght;

    return alphabet->at(resindex) + (isUpper? -32: 0);// return case back
}
int main() {
    int shift = 0;
    string alphabet = "abcde", newAlphabet, word;// always lower case
    cout << "Enter new alphabet: ";
    cin >> newAlphabet;
    if (newAlphabet.length() > 0)
        alphabet = newAlphabet;
    cout << "Enter the caesar shift: ";
    cin >> shift;
    cout << "Enter word: ";
    cin >> word;
    for (int i = 0, lenght = word.length(); i < lenght; i++)
        word[i] = getCaesar(&alphabet, word[i], shift);

    cout << "Result word: " << word << endl;
    main();
}