0048-Rotate-Image.py

'''
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 == n
matrix[i].length == n
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000
'''
class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)
        
        for i in range(n):
            j = i
            while j < n:
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
                j += 1
                
        for i in range(n):
            for j in range(n//2):
                matrix[i][j], matrix[i][n - 1 - j] = matrix[i][n - 1 - j], matrix[i][j]