题解 | #合法IP#

import java.util.Scanner;

// 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) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        String[] res = str.split("\\.");
        boolean ifValidation = true;
        if (res.length != 4) {
            ifValidation = false;
        } else {
            for (String re : res) {
                if (re.matches("^\\D.*") || re.length() == 0 || (re.startsWith("0") && re.length() > 1)) {
                    ifValidation = false;
                    break;
                }
                int num = Integer.parseInt(re);
                if (num < 0 || num > 255) {
                    ifValidation = false;
                    break;
                }
            }
        }
        if (ifValidation) System.out.println("YES");
        else System.out.println("NO");
    }
}