uva 11991 Easy Problem from Rujia Liu?

 1 #include <stdio.h>
 2 #include <map>
 3 #include <vector>
 4 using namespace std;
 5 
 6 map<int,vector<int> > a;
 7 
 8 int main()
 9 {
10     int n,m;
11 
12     while (scanf("%d%d",&n,&m) != EOF)
13     {
14         a.clear();
15 
16         for (int i = 0;i < n;i++)
17         {
18             int x;
19 
20             scanf("%d",&x);
21 
22             if (a.count(x)) a[x].push_back(i+1);
23             else
24             {
25                 a[x] = vector<int> ();
26 
27                 a[x].push_back(i+1);
28             }
29         }
30 
31         for (int i = 0;i < m;i++)
32         {
33             int k,v;
34 
35             scanf("%d%d",&k,&v);
36 
37             if (!a.count(v) || a[v].size() < k) printf("%d\n",0);
38             else printf("%d\n",a[v][k-1]);
39         }
40     }
41 
42     return 0;
43 }