CUBE-087: Finding Jedi

#include <bits/stdc++.h>
using namespace std;

long long ar[1000001];

int main(){

    int n;
    long long k;
    scanf("%d%lld",&n,&k);
    for(int i=1;i<=n;i++) {
        int x;
        scanf("%d",&x);
        ar[x]++;
    }

    long long ans=0;
    for(int i=0;i<=1000000;i++){
        int x=i,y=k-x;
        if(ar[x] < 1 or ar[y] < 1) continue;
        if(x == y){
            ans += (long long)(ar[x]*(ar[x]-1))/2;
            ar[x] = 0;
        }
        else {
            ans += ar[x]*ar[y];
            ar[x] = 0;
            ar[y] = 0;
        }
    }

    printf("%lld",ans);

    return 0;

}