# 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.
#
# Example 1:
#
# 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]
# ]
# Example 2:
#
# 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]
# ]
# matrix = [[1, 2, 3],
# [4, 5, 6],
# [7, 8, 9]]
# reverse= [[7, 8, 9],
# [4, 5, 6],
# [1, 2, 3]]
# output = [[7, 4, 1],
# [8, 5, 2],
# [9, 6, 3]]
顺时针旋转90°:
class Solution():
def rotate(self, matrix):
matrix.reverse()
for i in range(len(matrix)-1):
for j in range(i+1, len(matrix[0])):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
if __name__ == "__main__":
x = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]
Solution().rotate(x)
assert x == [[7, 4, 1],
[8, 5, 2],
[9, 6, 3]]
逆时针旋转90°:
class Solution():
def rotate(self, matrix):
for row in matrix:
row.reverse()
for i in range(len(matrix)-1):
for j in range(i+1, len(matrix[0])):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
if __name__ == "__main__":
x = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]
Solution().rotate(x)
assert x == [[3, 6, 9],
[2, 5, 8],
[1, 4, 7]]