Move all zeroes to end of array with minimum assignment operations

Question

Darko · Accepted Answer

public static void moveZeroesToEnd(int[] arr) {
    if (arr == null || arr.length == 0) return;

    int start = 0, end = arr.length - 1;

    while (start < end) {
        if (arr[start] == 0) {
            while (arr[end] == 0) {
                end--;
            }
            if (start < end) {
                swap(arr, start, end);
                end--;
            }
        }
        start++;
    }
}

Sushil · Answer

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    class Class1
    {
        public static void MoveAllZeroesToEnd(int []data)
        {
            // 1) skip all non-zeros at start
            // 2) skip all zeros at end
            // 3) move non-zero elements forward & 
            // 4) put zeroes at end
            int i1, i2, i3, i4;
            for (i1 = 0; i1  i1 && data[i2] == 0; i2--);
            if (i1 >= i2)
                return; // no work
            // i3 - non-zero elements index
            for (i4 = i1, i3 = i1; i4 <= i2; i4++)
            {
                // skip zeros;
                if (data[i4] == 0)
                    continue;
                data[i3++] = data[i4];
            }
            for (int i = i3; i <= i2; i++)
                data[i] = 0;
        }

        public static void printArray(int []data)
        {
            Console.WriteLine(string.Join(", ", data));
        }

        public static void Main()
        {
            int[][] data = {
                new int [] { 1, 2, 3, 0, 0, 0 },
                new int [] { 1, 2, 3 },
                new int [] { 1, 2, 0, 0, 3, 0, 0},
                new int [] { 1, 2, 0, 3, 0, 0, 4, 0, 0, 0 }
            };
            for (var i = 0; i < data.Length; i++)
            {
                Console.WriteLine("input {0}::", i + 1);
                printArray(data[i]);
                var input = (int [])data[i].Clone();
                MoveAllZeroesToEnd(input);
                Console.WriteLine("output {0}::", i + 1);
                printArray(input);
            }

        }
    }
}

anan · Answer

simple!

int f(int[] arr, int n)
{
    int e = n;
    for(int i = 0; i < e; i++)
    {
        if(arr[i] == 0)
        {
            e--;
            arr[i] = arr[e];
            arr[e] = 0;
            i--;
        }
    }
}

Krishna · Answer

Run two pointers through the array.  iterate first one to find the zero and other one to find the nonzero from the first pointer. Do exchange.  Till the second pointer reach end of array.

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