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  1. #include <iostream>
  2. using namespace std;
  3. #include <bits/stdc++.h>
  4.  
  5.  
  6. int  pairCal(int arr[],int k,int n)
  7.  {
  8.  
  9.     	int i,j,count=0,sum=0;
  10.  		for(i=0,j=n-1;i<n && j>=0;i++)
  11. 	     {
  12. 	 	sum=arr[i]+arr[j];
  13. 	 	while(sum>k && i!=j)
  14. 	 	 {
  15. 	 	 	j--;
  16. 	 	 	sum=arr[i]+arr[j];
  17. 	 	 }
  18. 	 	 if(i==j)
  19. 	 	  {
  20. 	 	  	break;
  21. 	 	  }
  22.  
  23. 	 	  count+=(j-i);
  24. 	     }
  25.  
  26. 	     return count;
  27.  }
  28.  
  29. int main() {
  30. 	// your code goes here
  31.  
  32. 	int arr[]={0,1,2,3,4,5,6};
  33. 	int n;
  34. 	cin>>n;
  35.  
  36.     sort(arr,arr+n);
  37. 	int left;
  38. 	cin>>left;
  39. 	int right;
  40. 	cin>>right;
  41.  
  42. 	int l=pairCal(arr,left-1,n);
  43. 	int r=pairCal(arr,right,n);
  44.  
  45. 	cout<<r-l;
  46.  
  47.  
  48. 	return 0;
  49. }
Success #stdin #stdout 0.01s 5284KB
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https://ideone.com/TOAxiR
language:
C++ (gcc 8.3)
created:
19 hours ago
visibility:
public

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