LeetCode. 矩阵置零（巧用数组首行首列存取信息，空间复杂度O(1)）

#include <vector>
using namespace std;
class Solution {
public:
	void setZeroes(vector<vector<int>>& matrix) {
		bool firstRowHasZero = false;
		bool firstColumnHasZero = false;
		//check the first column 
		for (int i = 0; i < matrix.size(); ++i) {
			if (matrix[i][0] == 0) {
				firstColumnHasZero = true;
				break;
			}
		}
		//check the first row
		for (int j = 0; j < matrix[0].size(); ++j) {
			if (matrix[0][j] == 0) {
				firstRowHasZero = true;
				break;
			}
		}
		//record the info in the first column and first row
		for (int i = 0; i < matrix.size(); i++)
		{
			for (int j = 0; j < matrix[i].size(); ++j) 
				if (matrix[i][j] == 0) {
					matrix[i][0] = 0;
					matrix[0][j] = 0;
				}
		}
		//start to set zero for vector from first row and frist column
		for (int i = 1; i < matrix.size(); i++)
		{
			if (matrix[i][0] == 0) {
				for (int j = 0; j < matrix[i].size(); j++)
					matrix[i][j] = 0;
			}
		}
		for (int j = 1; j < matrix[0].size(); j++)
		{
			if (matrix[0][j] == 0) {
				for (int i = 0; i < matrix.size(); i++)
					matrix[i][j] = 0;
			}
		}
		//set the first row and first column zeros
		if (firstRowHasZero) {
			for (int j = 0; j < matrix[0].size(); ++j) 
				matrix[0][j] = 0;
		}
		if (firstColumnHasZero) {
			for (int i = 0; i < matrix.size(); ++i) 
				matrix[i][0] = 0;
		}
		return;
	}
};