using System;

using System.Linq;                  

​

public class Program

{

    public static void Main()

    {

        TestSortZeros(new [] { 0, 0, 0, 1, 0, 2, 0, 3 });

        TestSortZeros(new [] { 1, 0, 2, 0, 3, 0, 0, 0 });

        TestSortZeros(new [] { 0, 0, 0, 1, 0, 2, 0, 3, 0, 0, 0 });

        TestSortZeros(new [] { 0, 0, 0 });

        TestSortZeros(new [] { 1, 2, 3 });

        TestSortZeros(new int[] { });

    }

​

    public static string ArrayToString(int[] array) => '[' + String.Join(',', array.Select(x => x.ToString())) + ']';

​

    public static void TestSortZeros(int[] array)

    {

        var original = ArrayToString(array);

        SortZeros(array);

        Console.WriteLine($"Result: {original} -> {ArrayToString(array)}");

    }

​

    public static void SortZeros(int[] array)

    {

        int dest = FindLastNonZeroPosition(array, array.Length);    

        if (dest == -1)

            return;

        for (int i = 0; i < array.Length; i++)

        {

            if (array[i] == 0) {

                Swap(ref array[i], ref array[dest]);

                dest = FindLastNonZeroPosition(array, dest);

                if (dest <= i + 1)

                    return;

            }

        }

    }

​

    public static int FindLastNonZeroPosition(int[] array, int index)

    {

        for (int i = index - 1; i >= 0; i--)

        {

            if (array[i] != 0)

                return i;

        }

        return -1;

    }

    public static void Swap(ref int x, ref int y)

    {

        var temp = x;

        x = y;

        y = temp;

    }

}

​