lc-48

//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 inp
//ut 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]]
// 
//
// 
// Constraints: 
//
// 
// n == matrix.length == matrix[i].length 
// 1 <= n <= 20 
// -1000 <= matrix[i][j] <= 1000 
// 
// Related Topics Array Math Matrix 
// 👍 10162 👎 521


//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public void rotate(int[][] matrix) {
        if (matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0) {
            return;
        }

        int i = 0, j = matrix.length - 1;

        while (i < j) {
            for (int k = 0; k < matrix[0].length; k++) {
                int temp = matrix[i][k];
                matrix[i][k] = matrix[j][k];
                matrix[j][k] = temp;
            }
            i++;
            j--;
        }

        for (i = 1; i < matrix.length; i++) {
            for (j = 0; j < i; j++) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = temp;
            }
        }
    }
}
//leetcode submit region end(Prohibit modification and deletion)