PHP Program for Reversal algorithm for right rotation of an array
Last Updated :
22 Jul, 2024
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Given an array, right rotate it by k elements.
After K=3 rotation
Examples:
Input: arr[] = {1, 2, 3, 4, 5,
6, 7, 8, 9, 10}
k = 3
Output: 8 9 10 1 2 3 4 5 6 7
Input: arr[] = {121, 232, 33, 43 ,5}
k = 2
Output: 43 5 121 232 33
Note: In the below solution, k is assumed to be smaller than or equal to n. We can easily modify the solutions to handle larger k values by doing k = k % n
Algorithm:
rotate(arr[], d, n)
reverseArray(arr[], 0, n-1) ;
reverse(arr[], 0, d-1);
reverse(arr[], d, n-1);
Below is the implementation of above approach:
<?php
// PHP program for right rotation of
// an array (Reversal Algorithm)
/*Function to reverse arr[]
from index start to end*/
function reverseArray(&$arr, $start, $end)
{
while ($start < $end)
{
$temp = $arr[$start];
$arr[$start] = $arr[$end];
$arr[$end] = $temp;
$start++;
$end--;
}
}
/* Function to right rotate arr[]
of size n by d */
function rightRotate(&$arr, $d, $n)
{
reverseArray($arr, 0, $n - 1);
reverseArray($arr, 0, $d - 1);
reverseArray($arr, $d, $n - 1);
}
/* function to print an array */
function printArray(&$arr, $size)
{
for ($i = 0; $i < $size; $i++)
echo $arr[$i] . " ";
}
// Driver code
$arr = array(1, 2, 3, 4, 5,
6, 7, 8, 9, 10);
$n = sizeof($arr);
$k = 3;
rightRotate($arr, $k, $n);
printArray($arr, $n);
// This code is contributed by ita_c
?>
Output
8 9 10 1 2 3 4 5 6 7
Complexity Analysis:
- Time Complexity: O(N)
- Auxiliary Space: O(1)
Please refer complete article on Reversal algorithm for right rotation of an array for more details!
