题解 | #验证IP地址#

一开始就想到正则表达式，但还是老老实实写了

import java.util.*;
import java.lang.*;

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
        if(isIPv4(IP))return "IPv4";
        else if(isIPv6(IP)){return "IPv6";}
        else return "Neither";
    }
    
    public boolean isIPv4(String IP){
        String[] str = IP.split("\\.");
        if(str.length<4)return false;
        
        for(int i=0;i<str.length;i++){
            if(str[i].startsWith("0"))return false;
            try{
                Integer num =Integer.parseInt(str[i]);
                if(num>255)return false;
            }catch(Exception e){
                return false;
            }
        }
        return true;
    }
    
    public boolean isIPv6(String IP){
        if(IP.endsWith(":") || IP.startsWith(":"))return false;
        String[] str = IP.split("\\:");
        if(str.length<8)return false;
        
        for(int i=0;i<str.length;i++){
            if(str[i].length()==0 || str[i].length()>4)return false;
            for(int j=0;j<str[i].length();j++){
                char c = str[i].charAt(j);
                boolean exp = (c>='0' && c<='9') || (c>='a' && c<='f') || (c>='A' && c<='F');
                if(!exp)return false;
            }
        }
        return true;
    }
}