problem_48.py

'''
Problem:
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.

Ex.
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]
]

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]
]

'''
from math import ceil

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        l = len(matrix)-1
        for i in range(int((l+1)/2)):
            for j in range(ceil((l+1)/2)):
                v1 = matrix[i][j]
                v2 = matrix[j][l-i]
                v3 = matrix[l-i][l-j]
                v4 = matrix[l-j][i]
                matrix[i][j] = v4
                matrix[j][l-i] = v1
                matrix[l-i][l-j] = v2
                matrix[l-j][i] = v3