C++ 查找字符串中第一个只出现一次的字符

#include <iostream>
#include <unordered_map>
using namespace std;

int main() {
    string s;
    cin >> s;
    unordered_map<char, int> count;
    for (char c : s) {
        count[c]++;
    }
    for (char c : s) {
        if (count[c] == 1) {
            cout << c << endl;
            return 0;
        }
    }
    cout << 'no' << endl;
    return 0;
}