整理一下。。

格式跑掉了 

import java.util.Scanner;

public class Bin {

public static void main(String []argv){

Scanner input = new Scanner(System.in);

while(input.hasNext()){

int city=input.nextInt(), num = input.nextInt();

boolean flag = false;

boolean[][] road = new boolean[city][city];

for(int x=0; x<num; x++){

int a=input.nextInt()-1, b=input.nextInt()-1;

road[a][b] = true;

}

int form=input.nextInt()-1, to=input.nextInt()-1;

boolean[] used = new boolean[city];

for(int x=0; x<city; x++){

if(road[form][to] == true){

System.out.println("Yes!!!");

flag = true;

break;

}

if(road[form][x]==true && used[x] != true){

used[x] = true;

for(int y=0; y<city; y++){

if(road[x][y]==true){

road[form][y] = true;

}

}

}

}

if(flag==false){

System.out.println("No!!!");

}

}

input.close();

}

}