Easy Problem from Rujia Liu? UVA - 11991

                Easy Problem from Rujia Liu?

  UVA - 11991 

题目链接：https://vjudge.net/problem/UVA-11991

题意：给定N个数与Q个询问，询问第k个等于a的数的下标

题解：用map存数，每次将数放进去，每个数的个数不定，用vector即可。

AC代码：

#include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
const int maxn = 1000005;
#define _for(i,a,b) for(int i=a;i<=b;i++)
map<int,vector<int> > Q;
int n,m;
int main(int argc, char const *argv[])
{
    while(cin>>n>>m)
    {
        Q.clear();
        _for(i,1,n)
        {
            int x;
            cin>>x;
            Q[x].push_back(i);
        }
        _for(i,1,m)
        {
            int x,y;
            cin>>x>>y;
            int k = Q[y].size();
            if(k<x)cout<<0<<endl;
            else cout<<Q[y][x-1]<<endl;
        }        
    }

    return 0;
}