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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 k=sc.nextInt();
  16. 		int a[]=new int[n];
  17. 		for(int i=0;i<n;i++)
  18. 		a[i]=sc.nextInt();
  19.  
  20. 		int count=0;
  21. 		// for(int i=0;i<n;i++)
  22. 		// {
  23. 		// 	for(int j=i+1;j<n;j++)
  24. 		// 	{
  25. 		// 		if(a[i]+a[j]==k)
  26. 		// 		count++;
  27. 		// 	}
  28. 		// }
  29.  
  30.  
  31. 		// optimisation
  32. 		Map<Integer,Integer> m=new HashMap<>();
  33. 		for(int ele:a)
  34. 		{
  35. 			int cpl=k-ele;
  36. 			if(m.containsKey(cpl))
  37. 			count+=m.get(cpl);
  38.  
  39. 			m.put(ele,m.getOrDefault(ele,0)+1);
  40. 		}
  41.  
  42. 		System.out.println(count);
  43.  
  44. 	}
  45. }
Success #stdin #stdout 0.14s 56684KB
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https://ideone.com/MJGaKI
language:
Java (HotSpot 12)
created:
15 days ago
visibility:
public

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