73. Set Matrix Zeroes

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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?

🧠 Thuật Toán & Kỹ Thuật

Matrix (Ma trận)
⏱️ Thời gian O(n²)
💾 Không gian O(n)

💻 Lời Giải

Python 0073-set-matrix-zeroes.py 
class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        r, c = len(matrix), len(matrix[0])
        save = []
        
        for i in range(r):
            for j in range(c):
                if matrix[i][j] == 0:
                    save.append((i, j))
                    
        for i, j in save:
            for x in range(r):
                matrix[x][j] = 0
            for y in range(c):
                matrix[i][y] = 0