leetcode: 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.
#
# click to show follow up.
#
# Follow up:
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# Did you use extra space?
# 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():
    def setZeroes(self, x):
        row, col = [0]*len(x), [0]*len(x[0])
        for i in range(len(x)):
            for j in range(len(x[0])):
                if x[i][j] == 0:
                    row[i], col[j] = 1, 1
        for i in range(len(x)):
            for j in range(len(x[0])):
                if row[i] == 1 or col[j] == 1:
                    x[i][j] = 0


if __name__ == "__main__":
    x = [[1, 0, 1, 1], [1, 1, 0, 1], [1, 1, 1, 0], [1, 1, 1, 1]]
    Solution().setZeroes(x)
    assert x == [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [1, 0, 0, 0]]