73. Set Matrix Zeroes

Given an _m_ x _n_ matrix. If an element is 0 , set its entire row and column to 0. Do it in-place.

Follow up:

• A straight forward solution using O( m n ) 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?

Example 1:

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

Example 2:

Input: matrix = [[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]]

Constraints:

• m == matrix.length
• n == matrix[0].length
• 1 <= m, n <= 200
• -231 <= matrix[i][j] <= 231 - 1

# @lc code=start
using LeetCode

function set_zeroes(matrix::Vector{Vector{Int}})::Vector{Vector{Int}}
    is_col = false
    m, n = length(matrix), length(matrix[1])

    for i = 1:m
        matrix[i][1] == 0 && (is_col = true)

        for j = 2:n
            matrix[i][j] == 0 && (matrix[i][1] = matrix[1][j] = 0)
        end
    end

    for i = 2:m, j = 2:n
        (matrix[i][1] == 0 || matrix[1][j] == 0) && (matrix[i][j] = 0)
    end

    # See if the first row needs to be set to zero as well
    if matrix[1][1] == 0
        for j = 1:n
            matrix[1][j] = 0
        end
    end

    # See if the first column needs to be set to zero as well
    if is_col
        for i = 1:m
            matrix[i][1] = 0
        end
    end

    return matrix
end
# @lc code=end

set_zeroes (generic function with 1 method)

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