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  1. #include <iostream>
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4. int qs11(vector<int>arr,int k1,int k2){
  5.     int n=arr.size();
  6.     vector<int>suffix(n,0);
  7.     vector<int>s(n,0);
  8.  
  9.     for(int k=0;k<n;k++){
  10.         int res=-1;
  11.         int low=k+1;
  12.         int high=n-1;
  13.         int req=k2-arr[k];
  14.         while(low<=high){
  15.             int mid=(low+high)/2;
  16.             if(arr[mid]>req){
  17.                 res=mid;
  18.                 high=mid-1;
  19.             }
  20.             else {
  21.                 low=mid+1;
  22.             }
  23.         }
  24.  
  25.         if(res!=-1){
  26.             s[k]=n-res;
  27.         }
  28.     }
  29.  
  30.     suffix[n-1]=s[n-1];
  31.     for(int i=n-2;i>=0;i--){
  32.         suffix[i]=s[i]+suffix[i+1];
  33.     }
  34.  
  35.     //Main logic of the code
  36.     int count=0;
  37.  
  38.     for(int i=1;i<n-2;i++){
  39.         int c1=0;
  40.         int low=0;
  41.         int high=i-1;
  42.         int req=k1-arr[i];
  43.         int r=-1;
  44.         while(low<=high){
  45.             int mid=(low+high)/2;
  46.             if(arr[mid]>req){
  47.                 r=mid;
  48.                 high=mid-1;
  49.             }
  50.             else{
  51.                 low=mid+1;
  52.             }
  53.         }
  54.         if(r!=-1){
  55.             c1=i-r;
  56.         }
  57.  
  58.         int c2=0;
  59.         c2=suffix[i+1];
  60.  
  61.         count+=c1*c2;
  62.     }
  63.  
  64.     return count;
  65. }
  66.  
  67. int main(){
  68.     int n;
  69.     cin>>n;
  70.     vector<int>arr(n);
  71.     for(int i=0;i<n;i++){
  72.         cin>>arr[i];
  73.     }
  74.     int k1,k2;
  75.     cin>>k1;
  76.     cin>>k2;
  77.  
  78.     int result=qs11(arr,k1,k2);
  79.     cout<<"The number of quadruplets from the array which satisfies the given condition: "<<result<<endl;
  80.     return 0;
  81.  
  82. }
Success #stdin #stdout 0s 5320KB
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stdin
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7
1 3 4 6 7 8 9
7
10
stdout
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The number of quadruplets from the array which satisfies the given condition: 10
https://ideone.com/yUH6wo
language:
C++ (gcc 8.3)
created:
1 day ago
visibility:
public

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