[Array]73. Set Matrix Zeroes

• 分类：Array
• 时间复杂度: O(m*n)
• 空间复杂度: O(1)

73. Set Matrix Zeroes

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?

代码：

O(1)空间解法：

class Solution:
    def setZeroes(self, matrix: 'List[List[int]]') -> 'None':
        """
        Do not return anything, modify matrix in-place instead.
        """
        fr,fc=False,False
        
        m=len(matrix)
        n=len(matrix[0])
        
        for i in range(m):
            if matrix[i][0]==0:
                fc=True
                break
        
        for i in range(n):
            if matrix[0][i]==0:
                fr=True
                break
                
        for i in range(1,m):
            for j in range(1,n):
                if matrix[i][j]==0:
                    matrix[i][0]=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 fc==True:
            for i in range(m):
                matrix[i][0]=0
        if fr==True:
            for i in range(n):
                matrix[0][i]=0
        

讨论：

1.看的youtube上篮子王的讲解，很清楚，受用