Saving James Bond - Easy Version

编程语言：Java
题目：

题解：写着写着一遍过了。
结果：AC

import java.io.*;
import java.util.Scanner;

public class Main {
    static StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    static PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
    static Scanner sc = new Scanner(new BufferedInputStream(System.in));

    static crocodile[] c;
    static boolean[] f;
    static double radius=7.5;
    static int n,d;

    public static void main(String[] args) throws IOException {
        n=sc.nextInt();
        d=sc.nextInt();
        c=new crocodile[n];
        f=new boolean[n];
        boolean flag=false;
        for(int i=0;i<n;i++){
            int x=sc.nextInt();
            int y=sc.nextInt();
            c[i]=new crocodile(x,y);
        }
        for(int i=0;i<n;i++){
            if(distance(i)&&dfs(i)){
                out.println("Yes");
                flag=true;
                break;
            }
        }
        if(!flag)
            out.println("No");
        out.flush();
    }

    private static boolean distance(int i) {
        if(Math.sqrt(c[i].x*c[i].x+c[i].y*c[i].y)<=d+radius)
            return true;
        else
            return false;
    }

    private static boolean distance(int i, int j) {
        int x=c[i].x-c[j].x;
        int y=c[i].y-c[j].y;
        if(Math.sqrt(x*x+y*y)<=d)
            return true;
        else
            return false;
    }

    private static boolean dfs(int i) {
        f[i]=true;
        if(Math.abs(c[i].x)>=50-d||Math.abs(c[i].y)>=50-d)
            return true;
        for(int j=0;j<n;j++){
            if(!f[j]&&distance(i,j)&&dfs(j)){
                return true;
            }
        }
        f[i]=false;
        return false;
    }
}
class crocodile{
    int x;
    int y;

    public crocodile(int x, int y) {
        this.x = x;
        this.y = y;
    }
}