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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 arr[]=new int [n];
  16.       for(int i=0;i<n;i++)
  17.       arr[i]=sc.nextInt();
  18.  
  19.       List<List<Integer>> adj=new ArrayList<>();
  20.       for(int i=0;i<=n;i++)
  21.       adj.add(new ArrayList<>());
  22.  
  23.       for(int i=0;i<n;i++)
  24.       {
  25.           int val=arr[i];
  26.           int ind=i;
  27.           adj.get(val).add(ind);
  28.       }
  29.  
  30.       System.out.println(adj);
  31. 	}
  32. }
Success #stdin #stdout 0.18s 56512KB
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5
2 2 3 4 1
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[[], [4], [0, 1], [2], [3], []]
https://ideone.com/e77rZH
language:
Java (HotSpot 12)
created:
4 hours ago
visibility:
public

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