48. Rotate Image

• categories: Code, Interview Question, leetcode, Medium
• source: https://leetcode.com/problems/rotate-image
• topics: 2D Array

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.

Idea:

for every row pop n last elements and insert them to the first index of corresponding row

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """ 
        for i in range(len(matrix)):
            for j in range(i, len(matrix) + i):
                matrix[len(matrix) - j + i - 1].insert(0, matrix[i].pop())