73. Set Matrix Zeroes

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class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        col0=1
        rows=len(matrix)
        cols=len(matrix[0])
        for i in range(rows):
            if matrix[i][0]==0:col0=0
            for j in range(1,cols):
                if matrix[i][j]==0:
                    matrix[i][0]=matrix[0][j]=0
        # print(matrix)
        for i in range(rows-1,-1,-1):
            for j in range(cols-1,0,-1):
                if matrix[i][0]==0 or matrix[0][j]==0:
                    matrix[i][j]=0
            if col0==0:matrix[i][0]=0

这个题，因为单独列出了col0，注意j的边界