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.
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] . " "; // This code is contributed // by ChitraNayal ?> |
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!
