XDU 1138 祯爷的苹果

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<iostream>
#include<map>
using namespace std;
map<long long ,long long> apple;
int main(void)
{
    long long n,m,t;
    cin>>t;
    while(t--)
    {
        scanf("%lld %lld",&n,&m);
        long long i,value;
        apple.clear();
        for(i=0;i<n;i++)
        {
            scanf("%lld",&value);
            apple[value]++;
        }
        long long ans=0;
        map<long long,long long>::iterator iter=apple.begin();
        for(;iter!=apple.end();iter++)
        {
            if(iter->first==m-iter->first)ans+=(iter->second)*(iter->second-1);
            else
                ans+=(iter->second)*(apple[m-iter->first]);
        }
        cout<<ans/2<<endl;
    }
    return 0;
}