题解 | #验证IP地址#

#include <cctype>
class Solution {
public:
    /**
     * 验证IP地址
     * @param IP string字符串 一个IP地址字符串
     * @return string字符串
     */
    bool isIPV4(string IP)
    {
        int n = IP.size();
        if(n == 0)
            return false;
        int spotcount = 0;
        int num = 0;
        if(IP[0] == '.')
            return false;
        for(int i = 0;i<n;++i)
        {
            if(i>0 && IP[i] == '.' && IP[i-1] == '.')
                return false;
            if(isalpha(IP[i]) || IP[i] == ':')
                return false;
            if(isalnum(IP[i]))
            {
                num = num * 10 + IP[i] - '0';
                if(num == 0)
                    return false;
            }
            if(IP[i] == '.')
            {
                spotcount++;
                if(num <= 0 || num > 255)
                    return false;
                num = 0;
            }
        }
        if(spotcount == 3)
            return true;
        else
            return false;
    }
    bool isIPV6(string IP)
    {
        int n = IP.size();
        if(n == 0)
            return false;
        int spotcount = 0;
        int size = 0;
        for(int i = 0;i<n;++i)
        {
            if(i>0 && IP[i] == ':' && IP[i-1] == ':')
                return false;
            if(isalpha(IP[i]))
            {
                if((IP[i] >= 'g' && IP[i] <= 'z') || (IP[i] >= 'G' && IP[i] <= 'Z'))
                    return false;
                    
            }
            if(IP[i] != ':')
            {
                size++;
            }
            else 
            {
                if(size > 4)
                    return false;
                size = 0;
                spotcount++;
            }
        }
        if(spotcount == 7)
            return true;
        else
            return false;
    }
    string solve(string IP) {
        // write code here
        if(isIPV4(IP))
            return "IPv4";
        else if(isIPV6(IP))
            return "IPv6";
        else
            return "Neither";
    }
};

解题思路：模拟