Alphabetical Addition (Codewars)

/*

Your task is to add up letters to one letter.

The function will be given a variable amount of arguments, each one being a letter to add.

Notes:
Letters will always be lowercase.
Letters can overflow (see second to last example of the description)
If no letters are given, the function should return 'z'
Examples:
add_letters('a', 'b', 'c') = 'f'
add_letters('a', 'b') = 'c'
add_letters('z') = 'z'
add_letters('z', 'a') = 'a'
add_letters('y', 'c', 'b') = 'd' # notice the letters overflowing
add_letters() = 'z'

*/


#include <iostream>
#include <map>
#include <algorithm>

using namespace std;

// Auxiliary Functions
// **************************************************************************************************************************
// **************************************************************************************************************************
// a) Converts a letter (such as 'd') ---> to an integer from 1 to 26 (such as 4)
int charToInt(char ch){
    map <char, int> myMap = map <char, int> ();
    int counter = 0;
    for(char i='a'; i<='z'; i++){
        counter++;
        myMap[i] = counter;
    }

    // Iterator creation
    map <char, int> :: iterator itr;
    for(itr=myMap.begin(); itr!=myMap.end(); itr++){
        if(itr->first == ch){
            return itr->second;
        }
    }

}

// b) Converts an integer (such as 4) ---> to a char (such as 'd')
char intToChar(int n){
    map <int, char> myMap = map <int, char> ();
    int counter = 0;
    for(char i='a'; i<='z'; i++){
        counter++;
        myMap[counter] = i;
    }

    // Iterator creation
    map <int, char> :: iterator itr;
    for(itr=myMap.begin(); itr!=myMap.end(); itr++){
        if(itr->first == n){
            return itr->second;
        }
    }

}

// **************************************************************************************************************************
// **************************************************************************************************************************
// 1. My Functions with no parameters
char add_letters(){
    return 'z';
}

// 2. My function with 1 parameter
char add_letters(char ch){
    return ch;
}

// 3. My function with 2 parameters
char add_letters(char ch1, char ch2){
    int num1 = charToInt(ch1);
    int num2 = charToInt(ch2);
    int num = (num1 + num2) % 26;
    return intToChar(num);
}

// 4. My function with 3 parameters
char add_letters(char ch1, char ch2, char ch3){
    char ch4 = add_letters(ch1, ch2);
    return add_letters(ch3, ch4);
}



// **************************************************************************************************************************
// **************************************************************************************************************************
// Main Function

int main()
{
    cout << "1.  No parameters:      add_letters() ---> " << "'" << add_letters() << "'" << endl;
    cout << "2.  With 1 parameter:   add_letters('e') ---> " << "'" << add_letters('e') << "'" << endl;
    cout << "3a. With 2 parameters:  add_letters('b','f') ---> " << "'" << add_letters('b', 'f') << "'" << endl;
    cout << "3b. With 2 parameters:  add_letters('x','d') ---> " << "'" << add_letters('x', 'd') << "'" << endl;
    cout << "4a. With 3 parameters:  add_letters('a','b', 'c') ---> " << "'" << add_letters('a', 'b', 'c') << "'" << endl;
    cout << "4b. With 3 parameters:  add_letters('b','d','y') ---> " << "'" << add_letters('b', 'd', 'y') << "'" << endl;
    cout << "4c. With 3 parameters:  add_letters('x','y','z') ---> " << "'" << add_letters('x', 'y', 'z') << "'" << endl;
}