题解 | #HJ090 合法IP#

import java.util.Scanner;

/**
 * HJ90 合法IP
 */
public class HJ090 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String str = sc.nextLine();
            String[] arr = str.split("\\.");
            if (arr.length != 4) {
                System.out.println("NO");
                return;
            }
            for (String s : arr) {
                try {
                    int n = Integer.parseInt(s);
                    if (n < 0 || n > 255) {
                        System.out.println("NO");
                        return;
                    }
                    if (s.length() > 1 && (s.startsWith("0") || s.startsWith("-") || s.startsWith("+"))) {
                        System.out.println("NO");
                        return;
                    }
                } catch (NumberFormatException e) {
                    System.out.println("NO");
                    return;
                }
            }
            System.out.println("YES");
        }
        sc.close();
    }
}