Hartly by for loop cycles and pseudo map

#include <iostream>
#include <vector>

struct myMapNode { // create our own structure map like type
    char letter;
    int count;
    std::string bitRepr; // binary representation of number in array
};

void addLetter(std::vector<myMapNode> &vec, char letterToAdd) { // create map like array and append elem if arr has no
                                                            // or update count to +1 if element is exists
    int len = vec.size();
    for (int i = 0; i < len; i++) {
        if (letterToAdd == vec[i].letter) {
            vec[i].count++;
            return;
        }
    }
    vec.push_back(myMapNode{letterToAdd, 1});
}

std::string convertToBin(int numCount, int n) { // bitRepr to bitRepr convert int 0 or 1 to char and add to our result string
    std::string output;
    for (int i = 0; i < numCount; i++) {
        output += ((char) n % 2) + 48; // %2 is 0 or 1 and is last num in bitRepr representation
        // +48 because 48 is position 0 in ascii
        n >>= 1; // bitRepr shift to new int
    }
    return output;
}

int bitsCount(int n) { // function for find max count of bits in out last index in array
    int count = 0;
    while (n) {
        count++;
        n >>= 1;
    }
    return count;
}

int main() {
    using namespace std;
    string str;
    getline(cin, str);
    vector<myMapNode> vec;
    for (auto letter: str) {
        addLetter(vec, letter);
    }

    int bitCount = bitsCount(vec.size() - 1); // find max count of bits in out last index in array

    for (int i = 0; i < vec.size(); ++i) {
        vec[i].bitRepr = convertToBin(bitCount, i);
        cout << vec[i].letter << " - " << vec[i].count << " - " << vec[i].bitRepr << '\n';
    }

    for (auto letter: str) { // print our string by finding in array equal letters
        for (int j = 0; j < vec.size(); j++) {
            if (vec[j].letter == letter) {
                cout << vec[j].bitRepr;
            }
        }
    }
    return 0;
}