XDU 1138 祯爷的苹果

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 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #include<string.h>
 4 #include<iostream>
 5 #include<map>
 6 using namespace std;
 7 map<long long ,long long> apple;
 8 int main(void)
 9 {
10     long long n,m,t;
11     cin>>t;
12     while(t--)
13     {
14         scanf("%lld %lld",&n,&m);
15         long long i,value;
16         apple.clear();
17         for(i=0;i<n;i++)
18         {
19             scanf("%lld",&value);
20             apple[value]++;
21         }
22         long long ans=0;
23         map<long long,long long>::iterator iter=apple.begin();
24         for(;iter!=apple.end();iter++)
25         {
26             if(iter->first==m-iter->first)ans+=(iter->second)*(iter->second-1);
27             else
28                 ans+=(iter->second)*(apple[m-iter->first]);
29         }
30         cout<<ans/2<<endl;
31     }
32     return 0;
33 }