LeetCode-in-All

73. Set Matrix Zeroes

Medium

Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0’s.

You must do it in place.

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

Follow up:

• A straightforward 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?

Solution

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var setZeroes = function(matrix) {
    const m = matrix.length
    const n = matrix[0].length
    let row0 = false
    let col0 = false

    for (let i = 0; i < m; i++) {
        if (matrix[i][0] === 0) {
            col0 = true
            break
        }
    }

    for (let j = 0; j < n; j++) {
        if (matrix[0][j] === 0) {
            row0 = true
            break
        }
    }

    for (let i = 1; i < m; i++) {
        for (let j = 1; j < n; j++) {
            if (matrix[i][j] === 0) {
                matrix[i][0] = 0
                matrix[0][j] = 0
            }
        }
    }

    for (let i = 1; i < m; i++) {
        for (let j = 1; j < n; j++) {
            if (matrix[i][0] === 0 || matrix[0][j] === 0) {
                matrix[i][j] = 0
            }
        }
    }

    if (col0) {
        for (let i = 0; i < m; i++) {
            matrix[i][0] = 0
        }
    }

    if (row0) {
        for (let j = 0; j < n; j++) {
            matrix[0][j] = 0
        }
    }
};

export { setZeroes }

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