// you can use includes, for example:
#include <algorithm>
#include <string>
#include <vector>


// 1. iterate on range A to B
// 2. convert int to string
// 3. count occurences of lovely numbers
// 4. return number


int solution(int A, int B)
{
    int cnt;
    std::string num_string;
    int lovely_cnt = 0;
    bool is_lovely;

    // iterates on range [A, B]
    for(int i = A ; i <= B ; i++)
    {
        bool is_lovely = true;
        cnt = 0;
        num_string = std::to_string(i);

        // must be lovely
        if(num_string.length() < 3)
        {
            lovely_cnt++;
            continue;
        }

        // checking number's loveliness
        for(int j = 0 ; j < num_string.length() ; j++)
        {
            cnt = std::count(num_string.begin(), num_string.end(), num_string[j]);
            if(cnt >= 3)
            {
                is_lovely = false;
                break;
            }
        }

        if(is_lovely)
        {
            lovely_cnt++;
        }
    }

    return lovely_cnt;
}