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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. 		int k=sc.nextInt();
  18.  
  19.  
  20. 		for(int i=1;i<=n;i++)
  21. 		b[i]=sc.nextInt();
  22.  
  23. 		int median =b[k];
  24.  
  25. 		for(int i=1;i<=n;i++)
  26. 		{
  27. 			if(b[i]<median)
  28. 			b[i]=-1;
  29. 			else if(b[i]==median)
  30. 			b[i]=0;
  31. 			else
  32. 			b[i]=1;
  33. 		}
  34.  
  35.  
  36. 		int prefix[]=new int[n+1];
  37. 		for(int i=1;i<=n;i++)
  38. 		prefix[i]=prefix[i-1]+b[i];
  39.  
  40. 		Map<Integer,Integer> freqeven=new HashMap<>();
  41. 		Map<Integer,Integer> freqodd=new HashMap<>();
  42. 		int count=0;
  43. 		freqeven.put(0,1);
  44.  
  45.  
  46. 		for(int i=1;i<=n;i++)
  47. 		{
  48.  
  49. 			/*  if i is odd then we need to check in even map because  if we want (j-i to be odd) if 
  50. 			i is odd then if we do odd(i) - even(j) then we will get(j-i) as odd length, so j must be even 
  51. 			hence we are checking in even map*/
  52.  
  53. 			if(i%2!=0)
  54. 			{
  55. 				count+=freqeven.getOrDefault(prefix[i],0);
  56. 				freqodd.put(prefix[i],freqodd.getOrDefault(prefix[i],0)+1);
  57.  
  58. 			}
  59. 			else
  60. 			{
  61. 				count+=freqodd.getOrDefault(prefix[i],0);
  62. 				freqeven.put(prefix[i],freqeven.getOrDefault(prefix[i],0)+1);
  63. 			}
  64. 		}
  65.  
  66. 		System.out.println(count);
  67.  
  68.  
  69.  
  70.  
  71. 	}
  72. }
Success #stdin #stdout 0.14s 54548KB
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https://ideone.com/Pb7K0d
language:
Java (HotSpot 12)
created:
7 days ago
visibility:
public

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