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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main(){
  5.     int n,m; cin>>n>>m;
  6.     vector<int> a(n); 
  7.     for(int i=0;i<n;i++) cin>>a[i];
  8.     sort(a.begin(),a.end());
  9.     long long cnt=0;
  10.     for(int i=0;i<n;i++){
  11.          int trai=i+1,phai=n-1,vitri=i;
  12.          while(trai<=phai){
  13.              int mid=(trai+phai)/2;
  14.              if(a[i]+a[mid]<=m){
  15.                  vitri=mid;
  16.                  trai=mid+1;
  17.              }
  18.              else phai=mid-1;
  19.          }
  20.          cnt+=vitri-i;
  21.     }
  22.     cout<<cnt;
  23.     return 0;
  24. }
  25.  
Success #stdin #stdout 0.01s 5304KB
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stdin
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5 6
1 2 3 4 5
stdout
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6
https://ideone.com/7GUJwf
language:
C++14 (clang 8.0)
created:
2 days ago
visibility:
public

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