题目
Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0’s, and return the matrix.
You must do it in place.
解题思路
方法1，使用一个数组存所有为0的位置，再遍历一次这个数组，更新所有位置
方法2，使用两个flag记录第一行和第一列是否有0，之后用第一行和第一列记录其他位置是否有0，最后更新整个矩阵
代码
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])
tmp = []
for i in range(m):
for j in range(n):
if matrix[i][j] == 0:
tmp.append([i, j])
for r, c in tmp:
for i in range(n):
matrix[r][i] = 0
for j in range(m):
matrix[j][c] = 0
class Solution:
def setZeroes(self, matrix: List[List[int]]) -> None:
"""
Do not return anything, modify matrix in-place instead.
"""
m = len(matrix)
n = len(matrix[0])
fm = fn = 1
for i in range(m):
if matrix[i][0] == 0:
fm = 0
break
for i in range(n):
if matrix[0][i] == 0:
fn = 0
break
for i in range(1, m):
for j in range(1, n):
if matrix[i][j] == 0:
matrix[i][0] = matrix[0][j] = 0
for i in range(1, m):
if matrix[i][0] == 0:
for j in range(1, n):
matrix[i][j] = 0
for j in range(1, n):
if matrix[0][j] == 0:
for i in range(1, m):
matrix[i][j] = 0
if fm == 0:
for i in range(m):
matrix[i][0] = 0
if fn == 0:
for i in range(n):
matrix[0][i] = 0
