pairs

http://acm.hdu.edu.cn/showproblem.php?pid=5178

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4888    Accepted Submission(s): 1758

Problem Description

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)

 

Input

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 x[i](−109≤x[i]≤109), means the X coordinates.

 

Output

For each case, output an integer means how many pairs<a,b> that |x[b]−x[a]|≤k.

 

Sample Input

2

5 5

-100

0

100

101

102

5 300

-100

0

100

101

102

 

Sample Output

3

10

 

Source

BestCoder Round #31

 

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二分水题

 #include <cstdio>

 #include <cstring>

 #include <string>

 #include <cmath>

 #include <iostream>

 #include <algorithm>

 #include <queue>

 #include <stack>

 #include <vector>

 #include <set>

 #include <map>

 typedef long long ll;

 #define maxn 100005

 #define lson l,mid,rt<<1

 #define rson mid+1,r,rt<<1|1

 using namespace std;

 ll n,k;

 ll a[maxn];

 int main(){

     int T;

     while(cin>>T){

         while(T--){

             cin>>n>>k;

             for(int i=;i<=n;i++){

                 cin>>a[i];

             }

             sort(a+,a+n+);

             ll ans=;

             int p;

             for(int i=;i<=n;i++){

                 p=lower_bound(a+,a+i,a[i]-k)-a;

                 ans+=i-p;

             }

             cout<<ans<<endl;

         }

     }

 }