题解 | #验证IP地址#

import java.util.*;


public class Solution {
    /**
     * 验证IP地址
     * @param IP string字符串 一个IP地址字符串
     * @return string字符串
     */
    public String solve (String IP) {
        // write code here
        String[] ip = IP.split("\\.");
//         System.out.println(ip.length);
//         for(int i = 0;i < ip.length;i++) {
//             System.out.println(ip[i]);
//         }
        if(ip.length == 4) {
            for(int i = 0;i < 4;i++) {
                for(int j = 0;j < ip[i].length();j++) {
                    if(ip[i].charAt(j) < '0' || ip[i].charAt(j) > '9') {
                        return "Neither";
                    }
                }
                int x = Integer.parseInt(ip[i]);
                if(x > 255) {
                    return "Neither";
                }
                if(ip[i].charAt(0) == '0' && ip[i].length() > 1) {
                    return "Neither";
                }
            }
            return "IPv4";
        }
        ip = IP.split("\\:");
//         System.out.println(ip.length);
//         for(int i = 0;i < ip.length;i++) {
//             System.out.println(ip[i]);
//         }
        for(int i = 0;i < 8;i++) {
            for(int j = 0;j < ip[i].length();j++) {
                if(!((ip[i].charAt(j) >= '0' && ip[i].charAt(j) <= '9') || (ip[i].charAt(j) >= 'a' && ip[i].charAt(j) <= 'e') || (ip[i].charAt(j) >= 'A' && ip[i].charAt(j) <= 'E'))) {
                    return "Neither";
                }
            }
            if(ip[i].length() == 0 || ip[i].length() > 4) {
                return "Neither";
            }
        }
        return "IPv6";
    }
}