HJ90 合法IP | 题解

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            String[] nums = in.next().split("\\.", -1);
            String res = "YES";
            if (nums.length == 4) {
                for (String num : nums) {
                    if (num.length() == 0 || num.length() > 3) {
                        res = "NO";
                        break;
                    }
                    if (num.charAt(0) == '0' && num.length() != 1) {
                        res = "NO";
                        break;
                    }
                    for (char ch : num.toCharArray()) {
                        if (!Character.isDigit(ch)) {
                            res = "NO";
                            break;
                        }
                    }
                    if (Integer.parseInt(num) > 255) {
                        res = "NO";
                        break;
                    }
                }
            } else
                res = "NO";
            System.out.println(res);
        }
    }
}