AIZU 2320 Infnity Maze

AIZU   2320   Infnity Maze       题目链接：http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=2320

题目大意：一个机器人，一张地图。地图上有机器人的初始位置，并用NSEW表示了朝向，'#'表示墙，'.'表示空地。每遇到不能走的地方（墙、边界）就向右拐。给出机器人要走的步数，问最后停在什么地方，朝向什么方向。

题目分析：DFS，vis要注意，加开一维朝向。如果走进了死胡同，会拐两次原路返回。剩下的就是无脑dfs了。

package May6thA;

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

static BigInteger one=BigInteger.ONE,two=new BigInteger("2"),zero=BigInteger.ZERO;
static String map[];
static BigInteger vis[][][];
static int h=1,w=1;
static boolean modswitch;
private static Node dfs(Node n){
//System.out.println(n.x+" "+n.y+" "+n.dir+" left=="+n.stepleft);
int d=0;
switch(n.dir){
case'N':d=0;break;
case'S':d=1;break;
case'E':d=2;break;
case'W':d=3;
}
if(n.stepleft.equals(zero))return n;
if(!vis[n.x][n.y][d].equals(zero)&&modswitch){
//System.out.println("mod=="+vis[n.x][n.y][d].subtract(n.stepleft));
n.stepleft=n.stepleft.mod(vis[n.x][n.y][d].subtract(n.stepleft));
modswitch=false;
}
else vis[n.x][n.y][d]=n.stepleft;
if(n.stepleft.equals(zero))return n;
while(!n.goable()){
//System.out.println("turning");
n.turn();
}
switch(n.dir){
case'N':return dfs(new Node(n.x-1,n.y,n.dir,n.stepleft.subtract(one)));
case'E':return dfs(new Node(n.x,n.y+1,n.dir,n.stepleft.subtract(one)));
case'S':return dfs(new Node(n.x+1,n.y,n.dir,n.stepleft.subtract(one)));
default:return dfs(new Node(n.x,n.y-1,n.dir,n.stepleft.subtract(one)));
}
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
BigInteger l=one;
while(h!=0||w!=0||!l.equals(zero)){
modswitch=true;
h=in.nextInt();
w=in.nextInt();
l=new BigInteger(in.next());
if(h==0&&w==0&&l.equals(zero))break;
vis=new BigInteger[h][w][4];
map=new String[h];
Node start = null;
//System.out.println(h+" "+w+" "+l);
in.nextLine();
for(int i=0;i<h;i++){
map[i]=in.nextLine();
//System.out.println(map[i]);
for(int j=0;j<w;j++){
char c=map[i].charAt(j);
for(int k=0;k<4;k++){
vis[i][j][k]=zero;
}
if(c!='.'&&c!='#'){
start=new Node(i,j,c,l);
map[i].replace(map[i].charAt(j),'.');
//System.out.println(i+" "+j+" "+c+" "+l);
}
}
}
start=dfs(start);
System.out.println((start.x+1)+" "+(start.y+1)+" "+start.dir);
}
}
static class Node{
int x,y;
char dir;
BigInteger stepleft;
public boolean goable(){
switch(this.dir){
case'N':return x>0&&map[x-1].charAt(y)!='#';
case'S':return x+1<h&&map[x+1].charAt(y)!='#';
case'E':return y+1<w&&map[x].charAt(y+1)!='#';
case'W':return y>0&&map[x].charAt(y-1)!='#';
}
return false;
}
private void turn(){
switch(this.dir){
case'N':this.dir='E';break;
case'S':this.dir='W';break;
case'E':this.dir='S';break;
case'W':this.dir='N';
}
}
public Node(int x,int y,char dir,BigInteger stepleft){
super();
this.x = x;
this.y = y;
this.dir = dir;
this.stepleft = stepleft;
}
}
}

PS：用java就是爽