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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		// your code goes here
  13. 		Scanner sc=new Scanner(System.in);
  14. 		int n=sc.nextInt();
  15. 		int b[]=new int[n+1];
  16.  
  17. 		for(int i=1;i<=n;i++)
  18. 		{
  19. 			b[i]=sc.nextInt();
  20. 		}
  21.  
  22. 		Map<Integer,Integer> m=new HashMap<>();
  23.  
  24. 		for(int k=3;k<n;k++)
  25. 		{
  26. 			for(int l=k+1;l<=n;l++)
  27. 			{
  28. 				int sum=b[k]+b[l];
  29. 				m.put(sum,m.getOrDefault(sum,0)+1);
  30. 			}
  31. 		}
  32.  
  33.  
  34. 		int ans=0;
  35.  
  36. 		for(int j=2;j<=n-2;j++)
  37. 		{
  38. 			for(int i=1;i<j;i++)
  39. 			{
  40. 				int sum=(b[i]+b[j]);
  41. 				if(m.containsKey(-sum))
  42. 				ans+=m.getOrDefault(-sum,0);
  43. 			}
  44. 			for(int j1=j+2;j1<=n;j1++)
  45. 			{
  46. 				int pair=b[j+1]+b[j1];
  47. 				m.put(pair,m.getOrDefault(pair,0)-1);
  48.  
  49. 			}
  50. 		}
  51.  
  52. 		System.out.println(ans);
  53. 	}
  54. }
Success #stdin #stdout 0.11s 54412KB
comments (?)
stdin
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7
1 2 3 4 -1 -2 -2
stdout
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3
https://ideone.com/3ERiOJ
language:
Java (HotSpot 12)
created:
6 days ago
visibility:
public

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