題目鏈接：

option=com_onlinejudge&Itemid=8&page=show_problem&problem=3142">https://uva.onlinejudge.org/index.php?

option=com_onlinejudge&Itemid=8&page=show_problem&problem=3142

題意：
給一個長度n的序列。有m詢問，每一個詢問會問第k個出現的數字的下標是多少
用map記錄

代碼：

#include <stdio.h>
#include <iostream>
 

#include <algorithm>
#include <string.h>
#include <queue>
#include <stack>
#include <map>

using namespace std;

int n, m;
map<int ,vector<int> > mp;

int c[1001000];

int main()
{
    while (~scanf("%d%d", &n, &m))
    {
        mp.clear();
        memset
 
(c, 0, sizeof(c));

        int tmp;
        for (int i = 1; i <= n; i++)
        {
            scanf("%d", &tmp);
            mp[tmp].push_back(i);
        }
        int a, b;
        while (m--)
        {
            scanf("%d%d", &a, &b);
            if (mp[b].size() < a) printf("0\n"
 
);
            else printf("%d\n", mp[b][a - 1]);
        }
    }
    return 0;
}

UVA 11991 Easy Problem from Rujia Liu?【STL】