poj2965解题报告

这道题目与poj1753的解题思路非常相似。

区别在于翻转的时候方式稍微不一样，不过这不影响算法的中心思想。

#include<iostream>

using namespace std;

bool refrigerator[5][5] = {false};

int step;
bool flag = false;


class node
{
public:
	int row;
	int col;
};

node steps[16+1];
bool judge_all()
{
	int i,j;
	for(i = 1;i<=4;i++)
		for(j = 1; j<=4;j++)
			if(refrigerator[i][j] == false)
				return false;

	return true;
}



void flip(int row,int col) 
{
	int i;
	for(i = 1;i<=4;i++)
	{
		refrigerator[i][col] = !refrigerator[i][col];
		refrigerator[row][i] = !refrigerator[row][i];
	}
	refrigerator[row][col] = !refrigerator[row][col];
}

void dfs(int row,int col,int deep)
{
	if(step == deep)
	{
		flag = judge_all();
		return;
	}

	if(row > 4 || flag ) return ;

	flip(row,col);

	// 将步伐记录在数组中
	steps[deep+1].row = row;
	steps[deep+1].col = col;

	if(col < 4)
		dfs(row,col+1,deep+1);
	else dfs(row+1,1,deep+1);

	flip(row,col);

	if(col< 4)
		dfs(row,col+1,deep);
	else dfs(row+1,1,deep);

	return;
	
}

int main()
{
	int i,j;
	char temp;
	
	for(i = 1;i<=4;i++)
		for(j = 1; j<=4 ; j++)
		{
			cin>>temp;
			if(temp == '-')
			refrigerator[i][j] = true;
		}

	for(step = 0; step <= 16 ; step ++)
	{
		dfs(1,1,0);
		if(flag) break;
	}

	if(flag)
		cout<<step<<endl;
	else cout<<"Impossible"<<endl;

	for(int q = 1;q<=step;q++)
		cout<<steps[q].row<<" "<<steps[q].col<<endl;

	//system("pause");
	return 0;
}