[Leetcode] 0048. Rotate Image

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You are given an nxn 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]]

Constraints:

n == matrix.length == matrix[i].length
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000

Table of contents

Python

				
					from typing import List # time complexity: O(n^2) # space complexity: O(n^2) class Solution: def rotate(self, matrix: List[List[int]]) -> None: ROW = len( matrix) COL = len(matrix[0]) newMatrix = [[0 for _ in range(COL)] for _ in range(ROW)] for r in range(ROW): for c in range(COL): newMatrix[ c][ROW - r - 1] = matrix[r][c] return # time complexity: O(n^2) # space complexity: O(1) class Solution: def rotate(self, matrix: List[List[ int]]) -> None: n = len(matrix) for r in range(n // 2): for c in range(r, n - r - 1): matrix[r][c], matrix[c ][n-1-r] = matrix[c][n-1-r], matrix[r][c] matrix[r][c], matrix[n-1-r][n-1 - c ] = matrix[n-1-r][n-1-c], matrix[r][c] matrix[r][c], matrix[n-1-c][r] = matrix[n-1 -c][r], matrix[r][c] return matrix 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))

Python

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