Question

How to rearrange an array and set arr[i] to arr[arr[index]] to index in Java

Answer 1

public class MyClass {
    public static void rearrange_array(int[] arr) {
        int size = arr.length;
        
        for (int i = 0; i < size; i++)
            arr[i] += (arr[arr[i]] % size) * size;
 
        for (int i = 0; i < size; i++)
            arr[i] /= size;
    }
    public static void main(String args[]) {
        int arr[] = {3, 5, 0, 2, 1, 4};
        
        // arr[arr[0]] = 2 -> arr[0] = 2
        // arr[arr[1]] = 4 -> arr[1] = 4
        // arr[arr[2]] = 3 -> arr[2] = 3
        // arr[arr[3]] = 0 -> arr[3] = 0
        // arr[arr[4]] = 5 -> arr[4] = 5
        // arr[arr[5]] = 1 -> arr[5] = 1

        rearrange_array(arr);
 
        for (int val: arr) {
            System.out.print(val + " ");
        }
    }
}



/*
run:

2 4 3 0 5 1 

*/

 

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