如何将矩阵顺时针旋转 90 度加速？

Question

将方阵旋转 90 度，复杂度为 O(1) space。我已经使用 Python 来解决它。我想知道我是否可以进一步改进我的代码。

def rotate_by_90(m):
  # unpacking arguments with zip(*) in reverse with [ : :-1]
  tuples = zip(*m[::-1])
  # flattening tuples to list with [list(i)]
  return [list(i) for i in tuples]

def makeMatrix(array, size):
  # validating size of matrix for given array
  if (size**2!=len(array)):
    return -1
  # make sub array of length size using array slicing  
  else:
    matrix = [array[i:i+size] for i in range(0, len(array), size)]
    return rotate_by_90(matrix)

arr = [1,2,3,4]
dimension = 2
result = makeMatrix(arr, dimension)
# Original Matrix: [[1, 2], [3, 4]]
# Result: [[3, 1], [4, 2]]

Answer 1

如果您追求的是速度，那么您使用的数组类型有误。您需要切换到 numpy 数组而不是列表。在 Numpy 中当然有一个函数用于这样的操作：rot90

Answer 2

不需要外部库或 zip。将其用于采访：

沿 x 轴翻转。
对角交换坐标

def rotate_by_90(m): a.reverse() for i in range(len(a)): for j in range(i): a[i][j], a[j][i] = a[j][i], a[i][j] return a

如何将矩阵顺时针旋转 90 度加速？

How can I speed-up a matrix rotation by 90 degrees clockwise?

python

arrays

rotation

matrix

python-3.x