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  1. #include <iostream>
  2. using namespace std;
  3. #include <bits/stdc++.h>
  4. int main() {
  5. 	// your code goes here
  6. 	int  n;
  7. 	cin>>n;
  8. 	 vector<int> arr(n + 1);
  9. 	int i=1;
  10. 	while(i<=n)
  11. 	 {
  12. 	 	cin>>arr[i];
  13. 	 	i++;
  14. 	 }
  15.  
  16.  
  17.       unordered_map<int,int>freq;
  18.  
  19.        for(int k=3;k<=n;k++)
  20.         {
  21.         	for(int l=k+1;l<=n;l++)
  22.         	 {
  23.         	 	freq[arr[k]+arr[l]]++;
  24.         	 }
  25.         }
  26. 	  int count =0;
  27. 	    for(int j=2;j<=n-2;j++)
  28. 	     {
  29. 	     	for(int i=1;i<j;i++)
  30. 	     	 {
  31. 	     	 	int g=-(arr[i]+arr[j]);
  32. 	     	 	count+=freq[g];
  33. 	     	 }
  34.  
  35. 	     	 for(int j1=j+2;j1<=n;j1++)
  36. 	     	  {
  37. 	     	  	freq[arr[j+1]+arr[j1]]--;
  38. 	     	  }
  39. 	     }
  40.  
  41.  
  42.  
  43. 	  cout<<count;
  44.  
  45. 	return 0;
  46. }
Success #stdin #stdout 0.01s 5288KB
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stdin
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7
1 2 3 4 -1 -2 -2
stdout
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3
https://ideone.com/LAo5lb
language:
C++ (gcc 8.3)
created:
1 day ago
visibility:
public

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