LeetCode刷题之路：59. 螺旋矩阵 II

给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

示例 1：

输入：n = 3
输出：[[1,2,3],[8,9,4],[7,6,5]]
示例 2：

输入：n = 1
输出：[[1]]

提示：

1 <= n <= 20

#最直观的思路

定义top,left,down,right分别代表四个边界，
随后依次按照四个方向开始遍历即可

class Solution:
    def generateMatrix(self, n: int) -> List[List[int]]:
        res = [[0] * n for _ in range(n)]
        top, left = 0,0
        down, right = n-1, n-1
        vaule = 1
        while(left <= right and top <= down):
            for i in range(left, right + 1):
                res[top][i] = vaule
                vaule += 1
            
            for i in range(top + 1, down + 1):
                res[i][right] = vaule
                vaule += 1
            
            for i in range(right - 1, left, -1):
                res[down][i] = vaule
                vaule += 1

            for i in range(down, top, -1):
                res[i][left] = vaule
                vaule += 1

            top += 1
            down -= 1
            left += 1
            right -= 1

            # print(res)
        return res