Set Matrix Zeroes

Given amxnmatrix, if an element is 0, set its entire row and column to 0. Do it in place.

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?

Tips:

先把除第一行和第一列之外每行是否需要归零记录在第一行和第一列上，之后再处理第一行和第一列。

Code：

public class Solution {
    public void setZeroes(int[][] matrix) {
        boolean firstRow = false, firstCol = false;
        int m = matrix.length, n = matrix[0].length;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == 0) {
                    matrix[0][j] = 0;
                    matrix[i][0] = 0;
                    if (i == 0) firstRow = true;
                    if (j == 0) firstCol = true;
                }
            }
        }
        for (int i = 1; i < m; i++) {
            if (matrix[i][0] == 0) {
                for (int j = 1; j < n; j++) matrix[i][j] = 0;
            }
        }
        for (int i = 1; i < n; i++) {
            if (matrix[0][i] == 0) {
                for (int j = 1; j < m; j++) matrix[j][i] = 0;
            }
        }
        if (firstRow) {
            for (int i = 0; i < n; i++) {
                matrix[0][i] = 0;
            }
        }
        if (firstCol) {
            for (int i = 0; i < m; i++) {
                matrix[i][0] = 0;
            }
        }
    }
}