rearrange the numbers such that arr[i] becomes arr[arr[i]].

class Rearrange  
{ 
    // The function to rearrange an array in-place so that arr[i] 
    // becomes arr[arr[i]]. 
    void rearrange(int arr[], int n)  
    { 
        // First step: Increase all values by (arr[arr[i]]%n)*n 
        for (int i = 0; i < n; i++) 
            arr[i] += (arr[arr[i]] % n) * n; 
  
        // Second Step: Divide all values by n 
        for (int i = 0; i < n; i++) 
            arr[i] /= n; 
    } 
  
    // A utility function to print an array of size n 
    void printArr(int arr[], int n)  
    { 
        for (int i = 0; i < n; i++) 
            System.out.print(arr[i] + " "); 
        System.out.println(""); 
    } 
  
    /* Driver program to test above functions */
    public static void main(String[] args)  
    { 
        Rearrange rearrange = new Rearrange(); 
        int arr[] = {3, 2, 0, 1}; 
        int n = arr.length; 
  
        System.out.println("Given Array is :"); 
        rearrange.printArr(arr, n); 
  
        rearrange.rearrange(arr, n); 
  
        System.out.println("Modified Array is :"); 
        rearrange.printArr(arr, n); 
    } 
} 
  
// This code has been contributed by Mayank Jaiswal