tj-7

#include <bits/stdc++.h>
using namespace std;
string find(int d, int b) {
    if (d == 0) {
        return "0";
    }
    string r = "";
    while (d > 0) {
        int re = d% b;
        if (re < 10){
            r += (char)(re + '0');
        } else {
            r += (char)(re - 10 + 'A');
        }
        d /= b;
    }
    reverse(r.begin(), r.end());
    return r;
}

int main() {
    string s;
    int b;
    cin >> s>> b;
    int d = stoi(s, nullptr, 2);
    
    string r = find(d, b);
    
    cout << r<< endl;
    return 0;
}

我有两种解法，但是这个更好理解