题解 | 字符统计

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

static struct CharNum {
    char ch;
    int count;
};


int main() {
    string s;
    while (cin >> s) {
        vector<CharNum> arr;
        for (const char c : s) {
            auto it = find_if(arr.begin(), arr.end(),
            [c](const CharNum & item) {
                return item.ch == c;
            });
            if (it != arr.end()) {
                it->count++;
            } else {
                arr.push_back({ c, 1 });
            }
        }
        sort(arr.begin(), arr.end(),
        [](const CharNum & a, const CharNum & b) {
            if (a.count == b.count) {
                return a.ch < b.ch;
            }
            return a.count > b.count;
        });

        for (auto item : arr) {
            cout << item.ch;
        }
        cout << endl;
    }

    return 0;
}