You are given an_n_x_n_2D matrix representing an image.
Rotate the image by90degrees (clockwise).

Have you met this question in a real interview?

Yes

Example

Given a matrix

[
    [1,2],
    [3,4]
]

rotate it by 90 degrees (clockwise), return

[
    [3,1],
    [4,2]
]

method 1

using the coordinates induct for the next position

1. have to come up with the originate point 0 <= r < (n + 1) / 2 and 0 <= c < n / 2
2. using the first induct for the next four points r, c => c, n - 1 - r => n - 1 - c, n - 1 - r => n - 1 - c, r

 def rotate(self, matrix):
        # write your code here
        if not matrix or not matrix[0]:
            return

        n = len(matrix)
        for r in range((n + 1) / 2):
            for c in range(n / 2):
                tmp = matrix[r][c]
                matrix[r][c] = matrix[n - 1 - c][r]
                matrix[n - 1 - c][r] = matrix[n - 1 - r][n - 1 - c]
                matrix[n - 1 - r][n - 1 - c] = matrix[c][n - 1 - r]
                matrix[c][n - 1 - r] = tmp