题解 | #合法IP#

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

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
       BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            String s = br.readLine();
            String[] split = s.split("\\.");
            if(split.length!=4){
                System.out.println("NO");
                return;
            }
            for (int i = 0; i < split.length; i++) {
                if(split[i].length()==0 || split[i].length()>3){
                    System.out.println("NO");
                    return;
                }
                for (int j = 0; j < split[i].length(); j++) {
                    if(!Character.isDigit(split[i].charAt(j))){
                        System.out.println("NO");
                        return;
                    }
                    if(Integer.valueOf(split[i]) >255){
                        System.out.println("NO");
                        return;
                    }
                    if(split[i].charAt(0) == '0' && split[i].length()!=1){
                        System.out.println("NO");
                        return;
                    }
                }
            }
            System.out.println("YES");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}