pairs

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

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <string>
 4 #include <cmath>
 5 #include <iostream>
 6 #include <algorithm>
 7 #include <queue>
 8 #include <stack>
 9 #include <vector>
10 #include <set>
11 #include <map>
12 typedef long long ll;
13 #define maxn 100005
14 #define lson l,mid,rt<<1
15 #define rson mid+1,r,rt<<1|1
16 using namespace std;
17 
18 
19 ll n,k;
20 ll a[maxn];
21 
22 int main(){
23 
24     int T;
25     while(cin>>T){
26         while(T--){
27             cin>>n>>k;
28             for(int i=1;i<=n;i++){
29                 cin>>a[i];
30             }
31             sort(a+1,a+n+1);
32             ll ans=0;
33             int p;
34             for(int i=2;i<=n;i++){
35                 p=lower_bound(a+1,a+i,a[i]-k)-a;
36                 ans+=i-p;
37             }
38 
39             cout<<ans<<endl;
40         }
41     }
42 
43 }

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