pku 1101 连连看

#include <iostream>
#include <queue>
#include <cmath>
using namespace std;

const int MAX_SIZE = 75;
int dir[4][2] = {{-1,0},{0,1},{1,0},{0,-1}};
class Point
{
public:
	int x,y,step,times;
};

class Game
{
public:
	void input(int,int);
	void order(int,int,int,int);
	int bfs();
private:
	int Width, Height;
	int lenof[MAX_SIZE+2][MAX_SIZE+2];
	bool hash[MAX_SIZE+2][MAX_SIZE+2];
	char map[MAX_SIZE+2][MAX_SIZE+2];
	Point Start, End;
};

void Game::input(int w, int h)
{
	int i, j;
	Width = w;
	Height = h;
	memset(hash, 0, sizeof(hash));
	for (i = 1; i <= w; ++i)
	{
		getchar();
		for (j = 1; j <= h; ++j)
		{
			scanf("%c", &map[i][j]);
			if (map[i][j] == 'X')
			{
				hash[i][j] = 1;
			}
		}
	}
}

void Game::order(int x1, int y1, int x2, int y2)
{
	Start.x = x1;
	Start.y = y1;
	End.x = x2;
	End.y = y2;
	memset(lenof, 4, sizeof(lenof));
	int t1 = hash[x1][y1];
	int t2 = hash[x2][y2];
	hash[x1][y1] = hash[x2][y2] = 0;
	int temp = bfs();
	if (temp == -1)
	{
		printf("impossible.\n");
	}
	else
	{
		printf("%d segments.\n", temp);
	}
	hash[x1][y1] = t1;
	hash[x2][y2] = t2;
}

int Game::bfs()
{
	int i;
	Point first, next;
	first = Start;
	first.times = 0;
	queue <Point> Q;
	for (i = 0; i < 4; ++i)
	{
		first.step = i;
		Q.push(first);
	}
	lenof[Start.x][Start.y] = 0;
	while (!Q.empty())
	{
		first = Q.front();
		Q.pop();
		
		for (i = 0; i < 4; ++i)
		{
			next.x = first.x + dir[i][0];
			next.y = first.y + dir[i][1];

			if (next.x >= 0 && next.x <= Width + 1 && next.y >= 0 && next.y <= Height + 1 
				&& !hash[next.x][next.y])
			{
				next.step = i;
				if (first.step == next.step)
				{
					if (first.times <= lenof[next.x][next.y])
					{
						lenof[next.x][next.y] = first.times;
						next.times = first.times;
						Q.push(next);
					}
				}
				else if (abs(first.step - next.step) != 2)
				{
					if (first.times + 1 <= lenof[next.x][next.y])
					{
						lenof[next.x][next.y] = first.times + 1;
						next.times = first.times + 1;
						Q.push(next);
					}
				}	
			}
		}
	}
	if (lenof[End.x][End.y] < 60000000)
	{
		return lenof[End.x][End.y] + 1;
	}
	else
	{
		return -1;
	}
}

int main()
{
	//freopen("1101.in","r",stdin);
	int a, b, cnt = 0;
	while (scanf("%d %d", &b, &a) != EOF && !(!a && !b))
	{
		Game g;
		g.input(a, b);
		printf("Board #%d:\n", ++cnt);
		int x1,x2,y1,y2;
		int cntcnt = 0;
		while (scanf("%d %d %d %d", &y1, &x1, &y2, &x2) && !(!x1 && !x2 && !y1 && !y2))
		{
			printf("Pair %d: ", ++cntcnt);
			g.order(x1,y1,x2,y2);
		}
		printf("\n");
	}
	return 0;
}