59.Spiral Matrix II

tags: Medium,Array,Matrix

59. Spiral Matrix II

題目描述

Given a positive integer n, generate an n x n matrix filled with elements from 1 to n² in spiral order.

範例

Example 1:

Input: n = 3
Output: [[1,2,3],[8,9,4],[7,6,5]]

Example 2:

Input: n = 1
Output: [[1]]

Constraints:

• 1 <= n <= 20

解答

Python

偷懶拿昨天的 code 改寫

class Solution:
    def generateMatrix(self, n: int) -> List[List[int]]:
        directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
        d = 0
        sx, sy = 0, 0
        matrix = [[0] * n for _ in range(n)]
        fill_val = 1
        matrix[sx][sy] = fill_val

        while fill_val < n * n:
            dx, dy = directions[d % 4]
            nx, ny = sx + dx, sy + dy

            if 0 <= nx < n and 0 <= ny < n and not matrix[nx][ny]:
                fill_val += 1
                matrix[nx][ny] = fill_val
                sx, sy = nx, ny
            else:
                d += 1

        return matrix

Ron ChenWed, May 10, 2023

Reference

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