Problem
Given a positive integer n, generate an n x n matrix filled with elements from 1 to n² in spiral order.
https://leetcode.cn/problems/spiral-matrix-ii/
Example 1:
Input: n = 3
Output: [[1,2,3],[8,9,4],[7,6,5]]
Example 2:
Input: n = 1
Output: [[1]]
Constraints:
Test Cases
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| class Solution:
def generateMatrix(self, n: int) -> List[List[int]]:
|
solution_test.py1
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| import pytest
from solution import Solution
@pytest.mark.parametrize('n, expected', [
(3, [[1,2,3],[8,9,4],[7,6,5]]),
(1, [[1]]),
])
@pytest.mark.parametrize('sol', [Solution()])
def test_solution(sol, n, expected):
assert sol.generateMatrix(n) == expected
|
Thoughts
跟 54. Spiral Matrix 类似，完全一样的遍历顺序，只是读出还是写入的区别。直接把代码搬过来，把 res[idx] = matrix[i][j] 替换成 matrix[i][j] = idx + 1，m 改成 n，基本就可以了。
Code
solution.py1
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| class Solution:
def generateMatrix(self, n: int) -> list[list[int]]:
matrix = [[0] * n for _ in range(n)]
steps = ((0, 1), (1, 0), (0, -1), (-1, 0))
limits = [n, n - 1]
i = 0
j = -1
dir = 0
move = 0
for idx in range(1, n * n + 1):
i += steps[dir][0]
j += steps[dir][1]
matrix[i][j] = idx
move += 1
if move == limits[dir & 1]:
limits[dir & 1] -= 1
dir = (dir + 1) % 4
move = 0
return matrix
|
