Question

How to sort an array of 0s, 1s and 2s in C#

Answer 1

using System;

class Program
{
    public static int swap(params int[] args) {
		return args[0];
	}

	private static void sort012Array(int[] arr) {
		int lo = 0;
		int curr = 0;
		int hi = arr.Length - 1;

		while (curr <= hi) {
			switch (arr[curr]) {
				case 0:
					arr[lo] = swap(arr[curr], arr[curr] = arr[lo]);
					lo++;
					curr++;
					break;
				case 1:
					curr++;
					break;
				case 2:
					arr[curr] = swap(arr[hi], arr[hi] = arr[curr]);
					hi--;
				    break;
			}
		}
	}
	
    static void Main() {
        int[] arr = new int[] {1, 2, 2, 0, 1, 1, 0, 2, 0, 1, 0, 0, 1};

		sort012Array(arr);

		for (int i = 0; i < arr.Length; i++) {
			Console.Write(arr[i] + " ");
		}
    }
}





/*
run:
  
0 0 0 0 0 1 1 1 1 1 2 2 2 
  
*/

 

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Answer 2

using System;

class Program
{
	static void Swap<T> (ref T a, ref T b) {
        T temp = a;
        a = b;
        b = temp;
    }

	private static void sort012Array(int[] arr) {
		int lo = 0;
		int curr = 0;
		int hi = arr.Length - 1;

		while (curr <= hi) {
			switch (arr[curr]) {
				case 0:
					Swap(ref arr[curr], ref arr[lo]);
					lo++;
					curr++;
					break;
				case 1:
					curr++;
					break;
				case 2:
					Swap(ref arr[hi], ref arr[curr]);
					hi--;
				    break;
			}
		}
	}
	
    static void Main() {
        int[] arr = new int[] {1, 2, 2, 0, 1, 1, 0, 2, 0, 1, 0, 0, 1};

		sort012Array(arr);

		for (int i = 0; i < arr.Length; i++) {
			Console.Write(arr[i] + " ");
		}
    }
}





/*
run:
  
0 0 0 0 0 1 1 1 1 1 2 2 2 
  
*/

 

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