UVA - 11624 Fire! BFS

题目大意：有一个迷宫着火了，这个迷宫里面有个人，这个人想要逃出迷宫，求最小的逃出距离是多少。人和火的走动的方向只有四个方向，上下左右

解题思路：要判断下一个点能不能走，就得先判断一下走下去后火会不会烧过来，所以在每次走之前，要先让火走，再让人走

#include<cstdio>
#include<cstring>
using namespace std;
#define maxn 1010
typedef struct status{
	int x,y,s,f;
	status(int X,int Y, int S, int F) {
		this->x = X;
		this->y = Y;
		this->s = S;
		this->f = F; 	
	}
	status() {}
}point;
char maze[maxn][maxn];
int vis[maxn][maxn];
point p[maxn*maxn];
int dir[4][2] = {{1,0},{-1,0},{0,1},{0,-1}};

void BFS(int R, int C) {

	int move = 0, F_move = 0;
	point J;
	for(int i = 0; i < R; i++)
		for(int j = 0; j < C; j++) {
			if(maze[i][j] == 'J')
				J = point(i,j,0,0);
			if(maze[i][j] == 'F') 
				p[F_move++] = point(i,j,0,1);
			vis[i][j] = 0;
		}

	vis[J.x][J.y] = 1;
	p[F_move++] = J;
	while(move < F_move) {
		point temp, now = p[move];
		if(!now.f) {
			if(now.x == 0 || now.x == R - 1|| now.y == 0 || now.y == C-1) {
				printf("%d\n",now.s+1);
				return ;
			}
		}
		for(int i = 0; i < 4; i++) {
			temp.x = now.x + dir[i][0];
			temp.y = now.y + dir[i][1];
			temp.s = now.s + 1;
			temp.f = now.f;	

			if(temp.x >= 0 && temp.x < R && temp.y >= 0 && temp.y < C)	 {
				if(maze[temp.x][temp.y] == '.') {
					if(temp.f) {
						maze[temp.x][temp.y] = 'F';
						p[F_move++] = temp;	
					}
					else if(!vis[temp.x][temp.y]) {
						p[F_move++] = temp;
						vis[temp.x][temp.y] = 1;
					}
				}
			}
		}
		move++;
	}
	printf("IMPOSSIBLE\n");
}

int main() {
	int test,R,C;
	while(scanf("%d",&test) != EOF ) {
		while(test--) {
			scanf("%d%d",&R, &C);
			for(int i = 0; i < R; i++)
				scanf("%s",maze[i]);
			BFS(R,C);
		}
	}
	return 0;
}