048--Rotate Image.md

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: void Do not return anything, modify matrix in-place instead.
        """
        #matrix[::] = zip(*matrix[::-1])
        
        n = len(matrix)
        for i in range(n//2):
            low = i; high = n-i-1
            for j in range(low,high,1):
                tmp = matrix[i][j]
                # left to top 
                matrix[i][j] = matrix[n-j-1][i]
                # bottom to left
                matrix[n-j-1][i] = matrix[n-i-1][n-j-1]
                # right to bottom
                matrix[n-i-1][n-j-1] = matrix[j][n-i-1]
                # top to right
                matrix[j][n-i-1] = tmp