pairs John has n points on the X axis, and their coordinates are (x[i],0),(i=0,1,2,…,n−1). He wants to know how many pairs<a,b> that |x[b]−x[a]|≤k.(a<b)
The first line contains a single integer T (about 5), indicating the number of cases. Each test case begins with two integers n,k(1≤n≤100000,1≤k≤109). Next n lines contain an integer xi, means the X coordinates.
For each case, output an integer means how many pairs<a,b> that |x[b]−x[a]|≤k.
题意：就是能找到多少对啊a[i],a[j] 满足 a[j] -a[i] <= k.;
思路：首先你肯定能想到要将其排序，然后得话，如果我们从小的开始找，就每次二分就行了！
代码语言：javascript复制#include<bits/stdc .h>
#define maxn 300000 100
using namespace std;
typedef long long ll;
int a[maxn];
int n,k;
int t;
ll num;
int bs(int l,int r,int tag){
int mid,ans=0;
while(l <= r && r < n){
mid = (l r)/2;
if(a[mid] <= tag){
ans = mid -l 1;
l = mid 1;
}
else{
r = mid - 1;
}
}
return ans;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>t;
while(t--){
num = 0;
cin>>n>>k;
for(int i=0;i<n;i ){
cin>>a[i];
}
sort(a,a n);
for(int i=0;i<n;i )
num = bs(i 1,n-1,a[i] k);
cout<<num<<endl;
}
}
