【搜索之BFS + 优先队列】杭电 hdu 1242 Rescue

/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
    Copyright (c) 2012 panyanyany All rights reserved.

    URL   : http://acm.hdu.edu.cn/showproblem.php?pid=1242
    Name  : 1242 Rescue

    Date  : Wednesday, April 4, 2012
    Time Stage : half an hour

    Result:
5703831	2012-04-04 16:03:27	Accepted	1242
31MS	304K	2294 B
C++	pyy

5703823	2012-04-04 16:02:46	Wrong Answer	1242
31MS	304K	2287 B
C++	pyy

5703801	2012-04-04 15:59:41	Wrong Answer	1242
31MS	304K	2280 B
C++	pyy

5703788	2012-04-04 15:57:34	Wrong Answer	1242
15MS	308K	2284 B
C++	pyy


Test Data :

Review :
题目描述是 "r" stands for each of Angel's friend. 一听到就心虚了，万一有几个朋友怎么办？于是应该以’a’为
起点，然后任意一个’r’为终点跳出。
//----------------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <vector>

#include <algorithm>
#include <iostream>
#include <queue>

using namespace std ;

#define MEM(a, v)        memset (a, v, sizeof (a))    // a for address, v for value
#define max(x, y)        ((x) > (y) ? (x) : (y))
#define min(x, y)        ((x) < (y) ? (x) : (y))

#define INF     (0x3f3f3f3f)
#define MAXN    (202)

#define DB    /##/
#define LL __int64

struct NODE {
	int x, y;
	int step;
	bool operator== (const NODE &nd) {
		return x == nd.x && y == nd.y;
	}
	bool operator< (const NODE &nd) const {
		return step > nd.step;	// 优先队列好像是按从大到小排序的……
	}
} ;

#define PATH(nd)	path[(nd).y][(nd).x]
#define MAP(nd)		map[(nd).y][(nd).x]
#define _RANGE(v, s, e)	((s) <= (v) && (v) < (e))
#define _IN(nd)		(_RANGE(nd.y, 0, n) && _RANGE(nd.x, 0, m))

const int dir[4][2] = {0,1, 0,-1, -1,0, 1,0};

char	map[MAXN][MAXN];

int		n, m;

NODE	beg, end;

void bfs()
{
	int i;
	priority_queue<NODE>	q;	// 不用优先队列就AC不了
	NODE	t, nn;

	end.step = INF;
	beg.step = 0;
	q.push(beg);
	while (!q.empty())
	{
		t = q.top();
		q.pop();

		for (i = 0; i < 4; ++i)
		{
			nn = t;
			nn.y += dir[i][0];
			nn.x += dir[i][1];

			if (!_IN(nn) || '#' == MAP(nn))
				continue;

			++nn.step;
			if ('r' == MAP(nn))	// 不知道是否有多个朋友，所以要及时跳出
			{
				end = nn;
				return ;
			}
			if ('.' != MAP(nn))	// 不敢确定守卫的符号是什么，所以只能这样了
			{
				++nn.step;		// 杀死守卫，时间+1
			}
			MAP(nn) = '#';
			q.push(nn);
		}
	}
}

int main()
{
	int i, j;
	while (scanf("%d %d", &n, &m) != EOF)
	{
		for (i = 0; i < n; ++i)
		{
			getchar();
			for (j = 0; j < m; ++j)
			{
				scanf("%c", &map[i][j]);
				if ('a' == map[i][j])
				{
					map[i][j] = '#';
					beg.y = i;
					beg.x = j;
				}
			}
		}
		bfs();
		if (INF == end.step)
			printf ("Poor ANGEL has to stay in the prison all his life.\n");
		else
			printf ("%d\n", end.step);
	}
	return 0;
}