Java Program to Move all zeroes to end of array (original) (raw)

Last Updated : 23 Jul, 2025

Given an array of random numbers, Push all the zero's of a given array to the end of the array. For example, if the given arrays is {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0}, it should be changed to {1, 9, 8, 4, 2, 7, 6, 0, 0, 0, 0}. The order of all other elements should be same. Expected time complexity is O(n) and extra space is O(1).
Example:

Input : arr[] = {1, 2, 0, 4, 3, 0, 5, 0}; Output : arr[] = {1, 2, 4, 3, 5, 0, 0};

Input : arr[] = {1, 2, 0, 0, 0, 3, 6}; Output : arr[] = {1, 2, 3, 6, 0, 0, 0};

There can be many ways to solve this problem. Following is a simple and interesting way to solve this problem.
Traverse the given array 'arr' from left to right. While traversing, maintain count of non-zero elements in array. Let the count be 'count'. For every non-zero element arr[i], put the element at 'arr[count]' and increment 'count'. After complete traversal, all non-zero elements have already been shifted to front end and 'count' is set as index of first 0. Now all we need to do is that run a loop which makes all elements zero from 'count' till end of the array.
Below is the implementation of the above approach.

Java `

/* Java program to push zeroes to back of array / import java.io.;

class PushZero { // Function which pushes all zeros to end of an array. static void pushZerosToEnd(int arr[], int n) { int count = 0; // Count of non-zero elements

    // Traverse the array. If element encountered is
    // non-zero, then replace the element at index 'count'
    // with this element
    for (int i = 0; i < n; i++)
        if (arr[i] != 0)
            arr[count++] = arr[i]; // here count is
                                   // incremented

    // Now all non-zero elements have been shifted to
    // front and 'count' is set as index of first 0.
    // Make all elements 0 from count to end.
    while (count < n)
        arr[count++] = 0;
}

/*Driver function to check for above functions*/
public static void main (String[] args)
{
    int arr[] = {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0, 9};
    int n = arr.length;
    pushZerosToEnd(arr, n);
    System.out.println("Array after pushing zeros to the back: ");
    for (int i=0; i<n; i++)
        System.out.print(arr[i]+" ");
}

} /* This code is contributed by Devesh Agrawal */

`

Output:

Array after pushing all zeros to end of array : 1 9 8 4 2 7 6 9 0 0 0 0

Time Complexity: O(n) where n is number of elements in input array.
Auxiliary Space: O(1)

Please refer complete article on Move all zeroes to end of array for more details!