LeetCode-in-All
189. Rotate Array
Medium
Given an array, rotate the array to the right by k steps, where k is non-negative.
Example 1:
Input: nums = [1,2,3,4,5,6,7], k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]
Example 2:
Input: nums = [-1,-100,3,99], k = 2
Output: [3,99,-1,-100]
Explanation:
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]
Constraints:
1 <= nums.length <= 105-231 <= nums[i] <= 231 - 10 <= k <= 105
Follow up:
- Try to come up with as many solutions as you can. There are at least three different ways to solve this problem.
- Could you do it in-place with
O(1)extra space?
Solution
class Solution {
private function reverse(&$nums, $l, $r) {
while ($l <= $r) {
$temp = $nums[$l];
$nums[$l] = $nums[$r];
$nums[$r] = $temp;
$l++;
$r--;
}
}
/**
* @param Integer[] $nums
* @param Integer $k
* @return NULL
*/
public function rotate(&$nums, $k) {
$n = count($nums);
$t = $n - ($k % $n);
$this->reverse($nums, 0, $t - 1);
$this->reverse($nums, $t, $n - 1);
$this->reverse($nums, 0, $n - 1);
}
}