力扣题库刷题笔记73--矩阵置零

**力扣题库刷题笔记73 -- 矩阵置零**

### 题目描述给定一个 `m x n` 的整数矩阵 `matrix` 和一个整数 `target`, 将所有元素等于 `target` 的行和列都设置为零。

**示例1:**

输入:`matrix = [[0,1,2,0],[3,4,5,2],[6,7,8,9],[4,1,0,3]]`, `target =1`

输出:`[[0,0,0,0],[3,4,5,2],[6,7,8,9],[4,1,0,3]]`

**示例2:**

输入:`matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]]`, `target =6`

输出:`[[1,2,3,4],[5,0,0,0],[9,0,0,0],[13,0,0,0]]`

### 解法#### 方法一:使用哈希表记录行和列索引

def setZeroes(matrix):
 m, n = len(matrix), len(matrix[0])
 rows, cols = set(), set()
 for i in range(m):
 for j in range(n):
 if matrix[i][j] ==0:
 rows.add(i)
 cols.add(j)
 for row in rows:
 matrix[row] = [0]*n for col in cols:
 for i in range(m):
 matrix[i][col] =0 return matrix

def setZeroes(matrix):
 m, n = len(matrix), len(matrix[0])
 rows = [False]*m cols = [False]*n for i in range(m):
 for j in range(n):
 if matrix[i][j] ==0:
 rows[i] = True cols[j] = True for i in range(m):
 for j in range(n):
 if rows[i] or cols[j]:
 matrix[i][j] =0 return matrix

def setZeroes(matrix):
 m, n = len(matrix), len(matrix[0])
 is_row_zero = False for i in range(m):
 if matrix[i][0] ==0:
 is_row_zero = True for j in range(1, n):
 if matrix[i][j] ==0:
 matrix[0][j] =0 matrix[i][0] =0 for i in range(m):
 for j in range(n):
 if matrix[i][0] ==0 or matrix[0][j] ==0:
 matrix[i][j] =0 return matrix