073-set-matrix-zeroes.py

"""
Problem Link: https://leetcode.com/problems/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?
"""
class Solution(object):
    def setZeroes(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        row = len(matrix)
        col = len(matrix[0])
        is_col= False
        for i in range(row):
            if matrix[i][0] == 0:
                is_col= True
            for j in range(1,col):
                if matrix[i][j] == 0:
                    matrix[0][j] = 0
                    matrix[i][0] = 0
                    
        for i in range(1,row):
            for j in range(1,col):
                if not matrix[i][0] or not matrix[0][j]:
                    matrix[i][j] = 0
        if matrix[0][0] == 0:
            for j in range(col):
                matrix[0][j] = 0
        if is_col:
            for i in range(row):
                matrix[i][0] = 0