image.png

思路：

  • 还是熟悉的递归，像洋葱一样，从外面往里面打印

  • 需要一开始初始化合适的数组大小

    代码：

    1. class Solution:
    2.   def __init__(self):
    3.       self.cur_val = 0
    5.   def externalMatrix(self, matrix: list(list()), left_pos: int, right_pos: int) -> None:
    6.       if left_pos > right_pos:
    7.           return
    9.       if left_pos == right_pos:
    10.           self.cur_val += 1
    11.           matrix[left_pos][right_pos] = self.cur_val
    13.       for index in range(left_pos, right_pos):
    14.           self.cur_val += 1
    15.           matrix[left_pos][index] = self.cur_val
    17.       for index in range(left_pos, right_pos):
    18.           self.cur_val += 1
    19.           matrix[index][right_pos] = self.cur_val
    21.       for index in range(right_pos, left_pos, -1):
    22.           self.cur_val += 1
    23.           matrix[right_pos][index] = self.cur_val
    25.       for index in range(right_pos, left_pos, -1):
    26.           self.cur_val += 1
    27.           matrix[index][left_pos] = self.cur_val
    29.       self.externalMatrix(matrix, left_pos + 1, right_pos - 1)
    31.   def generateMatrix(self, n: int) -> List[List[int]]:
    32.       matrix = list()
    33.       for _ in range(n):
    34.           matrix.append([])
    35.           for _ in range(n):
    36.               matrix[-1].append(0)
    38.       left_pos, right_pos = 0, n - 1 
    39.       self.externalMatrix(matrix, left_pos, right_pos)
    40.       return matrix