leetcode 2326. Spiral Matrix IV（python）

描述

You are given two integers m and n, which represent the dimensions of a matrix. You are also given the head of a linked list of integers. Generate an m x n matrix that contains the integers in the linked list presented in spiral order (clockwise), starting from the top-left of the matrix. If there are remaining empty spaces, fill them with -1.

Return the generated matrix.

Example 1:

Input: m = 3, n = 5, head = [3,0,2,6,8,1,7,9,4,2,5,5,0]
Output: [[3,0,2,6,8],[5,0,-1,-1,1],[5,2,4,9,7]]
Explanation: The diagram above shows how the values are printed in the matrix.
Note that the remaining spaces in the matrix are filled with -1.

Example 2:

Input: m = 1, n = 4, head = [0,1,2]
Output: [[0,1,2,-1]]
Explanation: The diagram above shows how the values are printed from left to right in the matrix.
The last space in the matrix is set to -1.

Note:

1 <= m, n <= 10^5
1 <= m * n <= 10^5
The number of nodes in the list is in the range [1, m * n].
0 <= Node.val <= 1000

解析

根据题意，给定两个整数 m 和 n ，它们代表矩阵的维数。给定一个整数链表的 head 。从矩阵的左上角开始，生成一个 m x n 矩阵，其中每个矩阵的位置以螺旋顺序（顺时针）呈现的链表中的整数。 如果还有剩余的空格，则用 -1 填充它们。返回生成的矩阵。

这道题就是在考察对二维数组的操作，我们只需要根据题意，顺时针模拟填充矩阵的过程即可完成题意，遍历每个元素进行填充不难，难点在与判断什么时候改变方向。

时间复杂度为 O(M*N) ，空间复杂度为 O(M*N) ，M 和 N 分别为矩阵的长和宽。

解答

class Solution(object):
    def spiralMatrix(self, m, n, head):
        """
        :type m: int
        :type n: int
        :type head: Optional[ListNode]
        :rtype: List[List[int]]
        """
        matrix = [[-1 for _ in range(n)] for _ in range(m)]
        dirs = [[0, 1], [1, 0], [0, -1], [-1, 0]]
        row, column = 0, 0
        d = 0
        while head:
            matrix[row][column] = head.val
            head = head.next
            nextR, nextC = row + dirs[d][0], column + dirs[d][1]
            if not (0 <= nextR < m and 0 <= nextC < n and matrix[nextR][nextC]==-1):
                d = (d + 1) % 4
            row, column = row + dirs[d][0], column + dirs[d][1]
        return matrix

运行结果

49 / 49 test cases passed.
Status: Accepted
Runtime: 2697 ms
Memory Usage: 104.4 MB

原题链接

leetcode.com/contest/wee…

您的支持是我最大的动力