「日常训练」 Fire!（UVA-11624）

与其说是训练不如说是重温。重新写了Java版本的代码。

import java.util.*;
import java.math.*;
import java.io.BufferedInputStream;

public class Main
{
    static class Node
    {
	int r, c, t;
	public Node(int _r, int _c)
	{
	    this(_r, _c, 0);
	}
	public Node(int _r, int _c, int _t)
	{
	    r=_r; c=_c; t=_t;
	}
    }

    static int[][] fireTime = new int[1005][1005];
    static int[][] maze = new int[1005][1005];
    static Queue<Node> q = new LinkedList<>();
    static final int[] dx = {0,1,0,-1};
    static final int[] dy = {1,0,-1,0};
    static int r, c;
    static int startR, startC;

    static void getFireTime()
    {
	for(int i=0;i<=r;++i)
	    for(int j=0;j<=c;++j)
		fireTime[i][j]=0x3f3f3f3f;
	while(!q.isEmpty())
	{
	    Node node = q.poll();
	    fireTime[node.r][node.c] = node.t;
	    for(int i=0; i!=4; ++i)
	    {
		int tr = node.r + dx[i],
		    tc = node.c + dy[i];
		if(tr>=0 && tr<r && tc>=0 && tc<c && fireTime[tr][tc]>node.t+1 && maze[tr][tc]==1)
		{
		    fireTime[tr][tc] = node.t+1;
		    q.offer(new Node(tr, tc, node.t+1));
		}
	    }
	}
    }
    static String solve()
    {
	Queue<Node> sq = new LinkedList<>();
	boolean[][] vis = new boolean[1005][1005];
	sq.offer(new Node(startR, startC));
	vis[startR][startC]=true;
	while(!sq.isEmpty())
	{
	    Node now = sq.poll();
	    if(now.t>=fireTime[now.r][now.c]) continue;
	    if(now.r==0 || now.r == r-1 || now.c == 0 || now.c == c-1)
		return String.valueOf(now.t+1);
	    for(int i=0;i!=4;++i)
	    {
		int tr = now.r + dx[i],
		    tc = now.c + dy[i];

		if(tr>=0 && tr<r && tc>=0 && tc<c && fireTime[tr][tc]>now.t+1 && (!vis[tr][tc]) && maze[tr][tc]==1)
		{
		    vis[tr][tc]=true;
		    sq.offer(new Node(tr, tc, now.t+1));
		}
	    }
	}
	return "IMPOSSIBLE";
    }
    public static void main(String args[])
    {
	Scanner cin = new Scanner(new BufferedInputStream(System.in));
	int T = cin.nextInt();
	while(T-- != 0)
	{
	    q.clear();
	    r = cin.nextInt();
	    c = cin.nextInt();
	    for(int i=0; i!=r; ++i)
	    {
		String str = cin.next();
		for(int j=0;j!=c;++j)
		{
		    char chr = str.charAt(j);
		    if(chr == '#') maze[i][j] = 0;
		    else if(chr == '.') maze[i][j] = 1;
		    else if(chr == 'J')
		    {
			maze[i][j] = 1;
			startR=i; startC=j;
		    }
		    else if(chr == 'F')
		    {
			maze[i][j] = 1;
			q.offer(new Node(i,j));
		    }
		}
	    }
	    getFireTime();
	    System.out.println(solve());
	}
    }
}