LeetCode-in-All
48. Rotate Image
Medium
You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.
Example 1:
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
Example 2:
Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
Example 3:
Input: matrix = [[1]]
Output: [[1]]
Example 4:
Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]
Constraints:
matrix.length == nmatrix[i].length == n1 <= n <= 20-1000 <= matrix[i][j] <= 1000
Solution
class Solution {
/**
* @param Integer[][] $matrix
* @return NULL
*/
public function rotate(&$matrix) {
$n = count($matrix);
for ($i = 0; $i < $n / 2; $i++) {
for ($j = $i; $j < $n - $i - 1; $j++) {
$pos = array(
array($i, $j),
array($j, $n - 1 - $i),
array($n - 1 - $i, $n - 1 - $j),
array($n - 1 - $j, $i)
);
$t = $matrix[$pos[0][0]][$pos[0][1]];
for ($k = 1; $k < count($pos); $k++) {
$temp = $matrix[$pos[$k][0]][$pos[$k][1]];
$matrix[$pos[$k][0]][$pos[$k][1]] = $t;
$t = $temp;
}
$matrix[$pos[0][0]][$pos[0][1]] = $t;
}
}
}
}