UVA 11991 Easy Problem from Rujia Liu? 简单STL

#include <iostream>
#include <cstdio>
#include <cstring>
#include <map>
using namespace std;

const int MAXN = 1e5 + 7;
map<int, int> cnt;
map<pair<int, int>, int> M;
int arr[MAXN];

int main() {
    int n, m;
    while( scanf( "%d%d", &n, &m ) != EOF ) {
        cnt.clear();
        M.clear();
        memset(arr, 0, sizeof(arr));
        for( int i = 1; i <= n; i++ ) {
            scanf( "%d", &arr[i]);
            if( cnt.count(arr[i]) == 0 ) {
                cnt.insert(make_pair(arr[i], 1));
                M.insert(make_pair(make_pair(1, arr[i]), i));
            }
            else {
                cnt[arr[i]]++;
                M.insert(make_pair(make_pair(cnt[arr[i]], arr[i]), i));
            }
        }
        for( int i = 1; i <= m; i++ ) {
            int times, num;
            scanf( "%d%d", &times, &num );
            printf( "%d\n", M[make_pair(times, num)]);
        }
    }
    return 0;
}