Skip to content

73. Set Matrix Zeroes

Difficulty Topics

Description

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

set-matrix-zeroes.py
class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """

        rows, cols = len(matrix), len(matrix[0])
        setCol0 = False

        for x in range(rows):
            setCol0 |= matrix[x][0] == 0
            for y in range(1, cols):
                if matrix[x][y] == 0:
                    matrix[x][0] = matrix[0][y] = 0

        for x in range(rows - 1, -1, -1):
            for y in range(1, cols):
                if matrix[x][0] == 0 or matrix[0][y] == 0:
                    matrix[x][y] = 0

            if setCol0: 
                matrix[x][0] = 0