59：螺旋矩阵II

问题描述

给定一个正整数 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正方形矩阵。

示例

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

问题分析

没啥好分析的，模拟一下旋转即可。

AC代码

class Solution:
    def generateMatrix(self, n: int):
        res = [[0 for i in range(n)] for i in range(n)]
        left = top = 0
        bottom = right = n
        flag = 1
        i = 1
        while i <= n*n:
            if flag == 1:
                for j in range(left,right):
                    res[top][j] = i
                    i += 1
                top += 1
                flag = 2
            elif flag == 2:
                for j in range(top,bottom):
                    res[j][right-1] = i
                    i += 1
                right -= 1
                flag = 3
            elif flag == 3:
                for j in range(right-1,left-1,-1):
                    res[bottom-1][j] = i
                    i += 1
                bottom -= 1
                flag = 4
            elif flag == 4:
                for j in range(bottom-1,top-1,-1):
                    res[j][left] = i
                    i += 1
                left += 1
                flag = 1
        return res
s = Solution()
s.generateMatrix(4)