题解 | 小红的不动点

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

int main() {
    int a, b;
    int n;
    map<int,int>map_A;
    cin >> n;
    vector<int> A(n,0);
    int i =0;

    while ( i < n) { // 注意 while 处理多个 case
        cin >> A[i] ;
        //cout << A[i] << endl;
        map_A[A[i]] ++;
        //cout <<A[i]<<" " << map_A[A[i]] <<endl;
        i++;
    }
    i = 0;
    /*while (i<n) {
        map_A[A[i]] +=1;
        i++;
    }*/
    i = 0;
    int sum = 0;
    while (i<map_A.size()) { 
        if (map_A[i] == i) {
            //cout <<map_A[i]<<"_" << i<<endl;
            sum += i;
        }
        i++;
    }
    cout << sum << endl;

    return 0;
}
// 64 位输出请用 printf("%lld")