题解 | 字符统计

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s;
    cin >> s;
    map<char, int> ma;
    vector<pair<int, char>> v;
    for (auto x: s) ma[x]++;
    for (auto [x, y]: ma) v.emplace_back(y, x);
    sort(v.begin(), v.end(), [&](pair<int, char> a, pair<int, char> b) {
        if (a.first != b.first) return a.first > b.first;
        else return a.second < b.second;
    });
    for (auto [x, y]: v) cout << y;
    cout << endl;
    return 0;
}