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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Ideone
  6. {
  7. 	public static void main (String[] args) throws java.lang.Exception
  8. 	{
  9. 		int[] array = {1,2,2,1,1,3,3,1,3};		
  10. 		Arrays.sort(array);
  11.  
  12. 		int pairs = 0; 
  13. 		int times = 1;
  14. 		for (int i = 1; i < array.length; i++) {
  15. 		    if (array[i] == array[i-1]) {
  16. 		        ++times;
  17. 		    } else {
  18. 		        pairs += times*(times-1) / 2;
  19. 		        times = 1;
  20. 		    }                   
  21. 		}
  22. 		pairs += times*(times-1) / 2;
  23. 		System.out.println(pairs);         		
  24. 	}
  25. }		
  26.  
Success #stdin #stdout 0.04s 4386816KB
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stdin 
Standard input is empty
stdout 
10
https://ideone.com/mu65ie
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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