LeetCode 48: Rotate Image
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.
https://leetcode.com/problems/rotate-image/description/
class Solution:
def rotate(self, matrix):
"""
:type matrix: List[List[int]]
:rtype: void Do not return anything, modify matrix in-place instead.
"""
N = len(matrix)
if N <= 1:
return
# 沿对角线对换
for i in range(N-1):
for j in range(i+1, N):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
# 左右对换
for i in range(N):
for j in range(N//2):
matrix[i][j], matrix[i][-(j+1)] = matrix[i][-(j+1)], matrix[i][j]
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