48. Rotate Image
Medium
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:
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:
- 1 <= strs.length <= 104
- 0 <= strs[i].length <= 100
- strs[i] consists of lowercase English letters.
Solution
class Solution:
def rotate(self, matrix: List[List[int]]) -> None:
"""
Do not return anything, modify matrix in-place instead.
"""
n = len(matrix)
# Flip the matrix horizontally
for i in range(n // 2):
matrix[i], matrix[n - 1 - i] = matrix[n - 1 - i], matrix[i]
# Then transpose the matrix
for i in range(n):
for j in range(i + 1, n):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]