PHP Program to Move All Zeroes to End of Array

Last Updated : 22 Jul, 2024

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 : [ 1, 2, 4, 3, 5, 0, 0 ]

Input : Arr = [ 1, 2, 0, 0, 0, 3, 6 ]
Output : [ 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.

PHP

<?php 
// A PHP program to move all
// zeroes at the end of array

// Function which pushes all 
// zeros to end of an array.
function pushZerosToEnd(&$arr, $n) {
  
    // Count of non-zero elements
    $count = 0; 

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

    // 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 Code
$arr = array(1, 9, 8, 4, 0, 0,
             2, 7, 0, 6, 0, 9);

$n = sizeof($arr);

pushZerosToEnd($arr, $n);

echo "Array after pushing all " .
     "zeros to end of array :";

for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";

?>

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!

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