BC#31.1001 pairs——二分

http://bestcoder.hdu.edu.cn/contests/contest_chineseproblem.php?cid=569&pid=1001

#include<iostream>
#include<cstring>
#include<cstdio>
#include<string>
#include<algorithm>
#include<set>
#include<map>
#include<cctype>
#include<cstdlib>
#define ll long long
const int maxn=1e5+10;
using namespace std;
int n,k;
int x[maxn];
ll ans;
int find(int a,int p){
    int l=p+1,r=n-1;
    while(l<=r){
        int mid=(l+r)>>1;
        if(abs((ll)a-x[mid])>k) r=mid-1;
        else  l=mid+1;
    }
    return r;
}
int main()
{
//freopen("in.cpp","r",stdin);
    int T;
    cin>>T;
    while(T--){
        scanf("%d%d",&n,&k);
        for(ll i=0;i<n;++i) scanf("%d",x+i);
        sort(x,x+n);
        ans=0;
        for(int i=0;i<n;++i){
            int tmp=find(x[i],i);
            ans+=(ll)tmp-i;
        }
        printf("%I64d\n",ans);
    }
    return 0;
}