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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. 		 int arr[] = {1, 5, 3, 4, 2}; int k =2; int count =0;
  13.             HashMap<Integer,Integer> map = new HashMap<>();
  14.             for(int j : arr){
  15.                 int  i1 = k-j; int i2 = k+j;
  16.                 if(map.containsKey(i1)){
  17.                     count+= map.get(i1);
  18.                 }
  19.                 if(map.containsKey(i2)){
  20.                     count+= map.get(i2);
  21.                 }
  22.                 map.put(j,map.getOrDefault(j,0)+1);
  23.             }
  24.             System.out.println("count => "+ count);	}
  25. }
Success #stdin #stdout 0.11s 53612KB
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stdin
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Standard input is empty
stdout
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count => 2
https://ideone.com/EiE5bV
language:
Java (HotSpot 12)
created:
14 days ago
visibility:
public

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