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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. 		Scanner sc = new Scanner(System.in);
  13. 		int size = sc.nextInt();
  14.  
  15. 		int[] arr =new int[size];
  16.  
  17. 		int target = sc.nextInt();
  18.  
  19. 		for(int i = 0;i<size;i++){
  20. 			arr[i] = sc.nextInt();
  21. 		}
  22.  
  23.  
  24.  
  25.             int result = countPairs(arr,target);
  26.             System.out.println(result);
  27.  
  28. 	}
  29.  
  30.     public  static int countPairs(int arr[], int target) {
  31.         // code here
  32.         Map<Integer,Integer> map = new HashMap<>();
  33.  
  34.         int count = 0;
  35.         for(int num : arr){
  36.  
  37.             int complement = target - num;
  38.  
  39.             if(map.containsKey(complement)){
  40.  
  41.                 count+=map.get(complement);
  42.  
  43.             }
  44.             map.put(num,map.getOrDefault(num,0)+1);
  45.         }
  46.  
  47.         return count;
  48.  
  49.     }
  50.  
  51. }
Success #stdin #stdout 0.11s 54484KB
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https://ideone.com/6357QY
language:
Java (HotSpot 12)
created:
3 days ago
visibility:
public

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