LeetCode 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:

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?

不占用多余的空间，首先确定第一行及第一列是否需要置0，再通过Matrix的第一行第一列记录该行或该列是否置0

创建两个布尔型变量来标记第一行及第一列是否需要置0

public class Solution {
    public void setZeroes(int[][] matrix) {
        int row = matrix.length;
		if (row == 0)
			return;
		boolean r=false,c=false;
		int col = matrix[0].length;
		for (int i = 0; i < row; i++)  //第一行
			if (matrix[i][0] == 0) 
				r=true;
		for (int j = 0; j < col; j++)  //第一列
			if (matrix[0][j] == 0) 
				c=true;
		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 j = 1; j < col; j++) {
			if (matrix[0][j] == 0)
				for (int i = 1; i < row; i++) {
					matrix[i][j] = 0;
				}
		}
		for (int i = 1; i < row; i++) {
			if (matrix[i][0] == 0)
				for (int j = 1; j < col; j++) {
					matrix[i][j] = 0;
				}
		}
		if (r) {  //对第一行置0
			for (int j = 0; j < row; j++)
				matrix[j][0] = 0;
			
		} 
		if(c){   //对第一列置0
			for (int i = 0; i < col; i++)
				matrix[0][i] = 0;
		}
    }
}