73. Set Matrix Zeroes

Description

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?

 

Solutions

Solution: Hash Map

• Time complexity: O(mn)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
const setZeroes = function (matrix) {
  const m = matrix.length;
  const n = matrix[0].length;
  const isFirstRowZero = matrix[0].includes(0);
  const isFirstColZero = matrix.some(row => row[0] === 0);

  for (let row = 1; row < m; row++) {
    for (let col = 1; col < n; col++) {
      if (matrix[row][col]) continue;

      matrix[row][0] = 0;
      matrix[0][col] = 0;
    }
  }

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

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

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