leetcode JAVA Set Matrix Zeroes 难度系数3 3.24

Question:

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:

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?

public class Solution {    public void setZeroes(int[][] matrix) {if (matrix.length < 1)return;boolean firstRow = false;boolean firstColumn = false;int row = matrix.length;int col = matrix[0].length;for (int i = 0; i < row; i++) {if (matrix[i][0] == 0) {firstColumn = true;break;}}for (int j = 0; j < col; j++) {if (matrix[0][j] == 0) {firstRow = true;break;}}for (int i = 1; i < row; i++) {for (int j = 1; j < col; j++) {if (matrix[i][j] == 0) {matrix[i][0] = 0;matrix[0][j] = 0;}}}for (int i = 1; i < row; i++) {for (int j = 1; j < col; j++) {if (matrix[i][0] == 0 || matrix[0][j] == 0) {matrix[i][j] = 0;}}}if (firstRow) {for (int j = 0; j < col; j++) {matrix[0][j] = 0;}}if (firstColumn) {for (int i = 0; i < row; i++) {matrix[i][0] = 0;}}}}