73.set-matrix-zeroes

Statement

简体中文English

Metadata

• Link: 矩阵置零
• Difficulty: Medium
• Tag: 数组 哈希表 矩阵

给定一个 m x n 的矩阵，如果一个元素为 0 ，则将其所在行和列的所有元素都设为 0 。请使用 原地 算法。

 

示例 1：

输入：matrix = [[1,1,1],[1,0,1],[1,1,1]]
输出：[[1,0,1],[0,0,0],[1,0,1]]

示例 2：

输入：matrix = [[0,1,2,0],[3,4,5,2],[1,3,1,5]]
输出：[[0,0,0,0],[0,4,5,0],[0,3,1,0]]

 

提示：

• m == matrix.length
• n == matrix[0].length
• 1 <= m, n <= 200
• -231 <= matrix[i][j] <= 231 - 1

 

进阶：

• 一个直观的解决方案是使用  O(mn) 的额外空间，但这并不是一个好的解决方案。
• 一个简单的改进方案是使用 O(m + n) 的额外空间，但这仍然不是最好的解决方案。
• 你能想出一个仅使用常量空间的解决方案吗？

Metadata

• Link: Set Matrix Zeroes
• Difficulty: Medium
• Tag: Array Hash Table Matrix

Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0's.

You must do it in place.

 

Example 1:

Input: matrix = [[1,1,1],[1,0,1],[1,1,1]]
Output: [[1,0,1],[0,0,0],[1,0,1]]

Example 2:

Input: matrix = [[0,1,2,0],[3,4,5,2],[1,3,1,5]]
Output: [[0,0,0,0],[0,4,5,0],[0,3,1,0]]

 

Constraints:

• m == matrix.length
• n == matrix[0].length
• 1 <= m, n <= 200
• -231 <= matrix[i][j] <= 231 - 1

 

Follow up:

• A straightforward solution using O(mn) space is probably a bad idea.
• A simple improvement uses O(m + n) space, but still not the best solution.
• Could you devise a constant space solution?

Solution

Python 3

from typing import List


class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        ld = {}
        cd = {}
        for i, l in enumerate(matrix):
            for j, c in enumerate(l):
                if c == 0:
                    ld[i] = True
                    cd[j] = True

        for i, l in enumerate(matrix):
            for j, c in enumerate(l):
                if (i in ld.keys() and ld[i]) or (j in cd.keys()) and cd[j]:
                    matrix[i][j] = 0

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最后更新: October 11, 2023