mirror of
https://github.com/prdlk/leetcode.git
synced 2026-09-16 23:16:26 +00:00
82 lines
2.0 KiB
Python
82 lines
2.0 KiB
Python
"""
|
|
73. Set Matrix Zeroes
|
|
Difficulty: Medium
|
|
https://leetcode.com/problems/set-matrix-zeroes/
|
|
|
|
──────────────────────────────────────────────────
|
|
|
|
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
|
|
|
|
• -2^31 <= matrix[i][j] <= 2^31 - 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?
|
|
"""
|
|
|
|
|
|
class Solution:
|
|
def setZeroes(self, matrix: List[List[int]]) -> None:
|
|
"""
|
|
Do not return anything, modify matrix in-place instead.
|
|
"""
|
|
m, n = len(matrix), len(matrix[0])
|
|
|
|
# 1. remember if row 0 or column 0 have their own zeros
|
|
row0_zero = any(matrix[0][c] == 0 for c in range(n))
|
|
col0_zero = any(matrix[r][0] == 0 for r in range(m))
|
|
|
|
# 2. use row 0 and column 0 as marker lists
|
|
for r in range(1, m):
|
|
for c in range(1, n):
|
|
if matrix[r][c] == 0:
|
|
matrix[r][0] = 0
|
|
matrix[0][c] = 0
|
|
|
|
# 3. zero the inner cells from the markers
|
|
for r in range(1, m):
|
|
for c in range(1, n):
|
|
if matrix[r][0] == 0 or matrix[0][c] == 0:
|
|
matrix[r][c] = 0
|
|
|
|
# 4. handle row 0 and column 0 last
|
|
if row0_zero:
|
|
for c in range(n):
|
|
matrix[0][c] = 0
|
|
if col0_zero:
|
|
for r in range(m):
|
|
matrix[r][0] = 0
|