"""Leetcode 48. Rotate Image
Medium

URL: https://leetcode.com/problems/rotate-image/

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:
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:
Given input matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],
rotate the input matrix in-place such that it becomes:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

Example 2:
Given input matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 
rotate the input matrix in-place such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]
"""


class Solution(object):
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: None Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)

        # For clockwise rotation, first reverse up to down.
        matrix.reverse()

        # Then swap along the diagonal for the left-bottom elements.
        for i in range(n):
            for j in range(i):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

        return matrix


def main():
    matrix = [
               [1,2,3],
               [4,5,6],
               [7,8,9]
             ]
    print Solution().rotate(matrix)

    matrix = [
               [ 5, 1, 9,11],
               [ 2, 4, 8,10],
               [13, 3, 6, 7],
               [15,14,12,16]
             ]
    print Solution().rotate(matrix)


if __name__ == '__main__':
    main()

"""Leetcode 48. Rotate Image
Medium

URL: https://leetcode.com/problems/rotate-image/

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:
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:
Given input matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],
rotate the input matrix in-place such that it becomes:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

Example 2:
Given input matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 
rotate the input matrix in-place such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]
"""


class Solution(object):
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: None Do not return anything, modify matrix in-place instead.

        Time complexity: O(n^2).
        Space complexity: O(1), since in-place.
        """
        n = len(matrix)

        # For clockwise rotation, first reverse up to down.
        matrix.reverse()

        # Then swap along the diagonal for the left-bottom elements.
        for i in range(n):
            for j in range(i):
                print i, j
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

        return matrix


def main():
    matrix = [
               [1,2,3],
               [4,5,6],
               [7,8,9]
             ]
    print Solution().rotate(matrix)

    matrix = [
               [ 5, 1, 9,11],
               [ 2, 4, 8,10],
               [13, 3, 6, 7],
               [15,14,12,16]
             ]
    print Solution().rotate(matrix)


if __name__ == '__main__':
    main()

Add time/space complexity