题解 | #验证IP地址#

/**
 * 验证IP地址
 * @param IP string字符串 一个IP地址字符串
 * @return string字符串
 */

char* ifIPv4(char* Ip);
char* ifIPv6(char* Ip);

char* solve(char* IP ) {
    int Temp = 0;
    while (IP[Temp] != '.' && IP[Temp] != ':')
        Temp++;
    if (IP[Temp] == '.')
        return ifIPv4(IP);
    else if (IP[Temp] == ':')
        return ifIPv6(IP);

    return "Error";
}


char* ifIPv4(char* Ip) {
    int Index = 0;
    int Val;
    int CountforDot = 0; //'.'的个数， '\0'也看作为一个'.'
    while (CountforDot < 4) {
        if (Ip[Index] == '0' && Ip[Index + 1] != '.' && Ip[Index + 1] != '\0')
            return "Neither";
        if(Ip[Index]=='.'||Ip[Index]=='\0')
            return "Neither";
        Val = 0;
        while (Ip[Index] != '.' && Ip[Index] != '\0') {
            Val = Val * 10 + Ip[Index] - '0';
            Index++;
        }
        CountforDot++;
        if (Val > 255)
            return "Neither";
        Index++;
    }

    if(Ip[Index-1]=='\0')
        return "IPv4";\
    else
        return "Neither";
}

char* ifIPv6(char* Ip) {
    int Index = 0;
    int Len;
    int CountforDot = 0; //':'的个数， '\0'也看作为一个':'
    while (CountforDot < 8) {
        if(Ip[Index]==':'||Ip[Index]=='\0')
            return "Neither";
        Len = 0;
        while (Ip[Index] != ':' && Ip[Index] != '\0') {
            if(('0'<=Ip[Index]&&Ip[Index]<='9') || ('a'<=Ip[Index]&&Ip[Index]<='f') || ('A'<=Ip[Index]&&Ip[Index]<='F') ){
            Len++;
            Index++;
            }
            else 
                return "Neither";
        }
        CountforDot++;
        if (Len > 4)
            return "Neither";
        Index++;
    }

    if(Ip[Index-1]=='\0')
        return "IPv6";\
    else
        return "Neither";
}