Question

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

Answer 1

using System;

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 = new int[] {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);

		foreach (int val in arr) {
			Console.Write(val + " ");
		}
	}
}




/*
run:
 
2 4 3 0 5 1 
 
*/

 

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