【Leetcode 数组】 螺旋矩阵 II（59）

题目

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 ]
]

解答

像搜索一样，定义一个表示上下左右移动的数组。可代码量，哭辽...

z = [
            [0, 1],  # 右
            [1, 0],  # 下
            [0, -1],  # 左
            [-1, 0]  # 上
        ]

代码实现：

class Solution:
    # Time: O(N)，N为数值个数
    def generateMatrix(self, n):
        if n == 0:
            return []
        ans = [[-1]*n for _ in range(n)]  # 初始化为-1
        z = [
            [0, 1],  # 右
            [1, 0],  # 下
            [0, -1],  # 左
            [-1, 0]  # 上
        ]
        x = y = 0
        cur = 1
        while -1 in ans[n//2]:
            if ans[x][y] == -1:
                ans[x][y] = cur
                cur += 1
            while x + z[0][0] < n and y + z[0][1] < n and ans[x+z[0][0]][y+z[0][1]] == -1:  # 向右
                x = x + z[0][0]
                y = y + z[0][1]
                ans[x][y] = cur
                cur += 1
            while x + z[1][0] < n and y + z[1][1] < n and ans[x+z[1][0]][y+z[1][1]] == -1:  # 向下
                x = x + z[1][0]
                y = y + z[1][1]
                ans[x][y] = cur
                cur += 1
            while x + z[2][0] < n and y + z[2][1] < n and y + z[2][1] >= 0 and ans[x+z[2][0]][y+z[2][1]] == -1:  # 向左
                x = x + z[2][0]
                y = y + z[2][1]
                ans[x][y] = cur
                cur += 1
            while x + z[3][0] < n and x + z[3][0] >= 0 and y + z[3][1] < n and ans[x+z[3][0]][y+z[3][1]] == -1:  # 向上
                x = x + z[3][0]
                y = y + z[3][1]
                ans[x][y] = cur
                cur += 1
        return ans


s = Solution()
ans = s.generateMatrix(3)
print(ans)


# [
#  [ 1, 2, 3 ],
#  [ 8, 9, 4 ],
#  [ 7, 6, 5 ]
# ]