回环矩阵 python

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编程输出以下格式的数据。
When i=0
1

When i=1

7 8 9
6 1 2
5 4 3

When i=2

21 22 23 24 25
20 7 8 9 10
19 6 1 2 11
18 5 4 3 12
17 16 15 14 13

def rotation_matrix(n):
    arr = [[None for _ in range(n)] for _ in range(n)]
    right, down, left, up = n - 1, n - 1, 0, 0
    i, j = n - 1, 0  # i是行，j是列
    sum_ = n * n
    while sum_ > 0:
        # left
        for j in range(right, left - 1, -1):
            arr[i][j] = sum_
            sum_ -= 1
        left += 1
        # up
        for i in range(down - 1, up - 1, -1):
            arr[i][j] = sum_
            sum_ -= 1
        up += 1
        # right
        for j in range(left, right + 1):
            arr[i][j] = sum_
            sum_ -= 1
        right -= 1
        # down
        for i in range(up, down):
            arr[i][j] = sum_
            sum_ -= 1
        down -= 1
    return arr


if __name__ == '__main__':
    n = int(input('input:'))
    arr = rotation_matrix(n)
    for row in range(n):
        print(arr[row])

• 结果：

/Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6 /Users/daidai/Desktop/刷题.py
input:5
[17, 16, 15, 14, 13]
[18, 5, 4, 3, 12]
[19, 6, 1, 2, 11]
[20, 7, 8, 9, 10]
[21, 22, 23, 24, 25]

Process finished with exit code 0