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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.       for(int l=4;l<=n;l++)
  19.        {
  20.        	freq[arr[l]]++;
  21.        }
  22.        int count=0;
  23.        for(int i=1;i<=n;i++)
  24.         {
  25.         	for(int j=i+1;j<=n;j++)
  26.         	 {
  27.         	 	for(int k=j+1;k<=n-1;k++)
  28.         	 	 {
  29.         	 	 	int g=-(arr[i]+arr[j]+arr[k]);
  30.         	 	 	count=count+freq[g];
  31.         	 	 	freq[arr[k+1]]--;
  32.         	 	 }
  33.         	 	 for(int z=j+3;z<=n;z++)
  34.         	 	  {
  35.         	 	  	freq[arr[z]]++;
  36.         	 	  }
  37.         	 }
  38.         }
  39.  
  40.  
  41.  
  42. 	  cout<<count;
  43.  
  44. 	return 0;
  45. }
Success #stdin #stdout 0s 5288KB
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stdin
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7
1 2 3 4 -1 -2 -2
stdout
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2
https://ideone.com/JwXlVW
language:
C++ (gcc 8.3)
created:
6 hours ago
visibility:
public

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