Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.

Example 1:

Input: 
[
  [1,1,1],
  [1,0,1],
  [1,1,1]
]
Output: 
[
  [1,0,1],
  [0,0,0],
  [1,0,1]
]

Example 2:

Input: 
[
  [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]
]
 

Follow up:

• A straight forward 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?

 1 class Solution(object):
 2     def setZeroes(self, matrix):
 3         """
 4         :type matrix: List[List[int]]
 5         :rtype: None Do not return anything, modify matrix in-place instead.
 6         """
 7         if not matrix:
 8             return matrix   
 9         row, cloum = len(matrix), len(matrix[0])
 
10         tem_row, tem_cloum = set(), set()
11         for i in range(row):       #遍歷矩陣得到0的行坐標和列左邊
12             for j in range(cloum): 
13                 if matrix[i][j] == 0:
14                     tem_row.add(i)
15                     tem_cloum.add(j)
16         self.set_zero(matrix, tem_row, tem_cloum)   # 進行0設置
17                      
22     def set_zero(self, matrix, tem_row, tem_cloum):
23         for row  in tem_row:       # 設置列
24             for i in range(len(matrix[0])):
25                 if matrix[row][i] != 0:
26                     matrix[row][i] = 0
27         for cloum  in tem_cloum:      # 設置行
28             for j in range(len(matrix)):
29                 if matrix[j][cloum] != 0:
30                      matrix[j][cloum] = 0

常量空間的解法

　　詳細解釋鏈接：https://leetcode.com/problems/set-matrix-zeroes/solution/

 1 class Solution(object):
 2     def setZeroes(self, matrix):
 3         """
 4         :type matrix: List[List[int]]
 5         :rtype: void Do not return anything, modify matrix in-place instead.
 6         """
 7         is_col = False
 8         R = len(matrix)
 9         C = len(matrix[0])
10         for i in range(R):      # 遍歷矩陣，得到元素為0的地址，並設置該列和該行起始位置為0，
11             if matrix[i][0] == 0:
12                 is_col = True
13             for j in range(1, C):
14                 if matrix[i][j]  == 0:   
15                     matrix[0][j] = 0
16                     matrix[i][0] = 0
17 
18    
19         for i in range(1, R):         # 根據行的開頭和列的開頭來設置剩余部分的元素值
20             for j in range(1, C):
21                 if not matrix[i][0] or not matrix[0][j]:
22                     matrix[i][j] = 0
23      
24         if matrix[0][0] == 0:       # 判斷起始位置是否為0
25             for j in range(C):
26                 matrix[0][j] = 0
27 
28         if is_col:               # 第一列全為0
29             for i in range(R):
30                 matrix[i][0] = 0

【LeetCode每天一題】Set Matrix Zeroes(設置0矩陣)