Check if string is valid IPv4 ip address

Given a string, we need to print whether the string is a valid IPv4 ip address or not. For example, 12.2.3.4 is valid IP address and 1222.2.22.33 is not.
The key steps in writing an verifyIP function are:

• Length of the string should be less than equal to 15. As each sub part of the IP can be at max 3 digits and we can have at max 3 dots.
• The string should have 4 parts separated by 3 dots.
• Each part should be greater than 0 and less than 256.

void verifyIP(char *s )
{
    int count=0;
    char *str = new char[strlen(s)];
    strcpy(str,s);

    //Check if length of string is greater than 15.
    if(strlen(str)>15)
    {
        cout<<"Not an IP Address"<<endl;
        return;
    }
    
    char *ip=strtok(str,".");
    
    while(ip!=NULL)
    {
        count++;

        //Check that each subpart is less than 256
        if(atoi(ip)>255)
        {
            cout<<"Not an IP address"<<endl;
            return;
        }
        ip=strtok(NULL,".");
    }

    //Check that we have 4 parts in the ip
    if(count==4)
        cout<<"Correct IP Address"<<endl;
    else
        cout<<"Not an IP Address"<<endl;
}

Implement strtok()

strtok takes in a string and one or more tokens, and it returns a substring which is split using all the tokens provided. The tricky part is that once you call strtok with a string, next time you can call it and pass NULL instead of any string and it will assume the string you passed in previous call.
The key steps in writing an atoi function are:

• Make a static copy of the string passed into the function for reuse on next function call.
• If new string is passed to function, make a copy of it else reuse the last sent string.
• Check for tokens in the string to split on. Make sure to keep track of end of string.
• Update the saved copy of string as well as the string passed into the function.

char* new_strtok(char* str, const char* tokens)
{
    //Making a static string to be used again on next function call.
    static char *temp;
    
    //If string passed to function is not null, copy it to our static variable
    if(str!=NULL)
    {
        temp=(char*)malloc(strlen(str));
        strcpy(temp,str);
    }

    //If the string passed is NULL and even the copy is NULL, we are done and return NULL.
    else if(temp==NULL)
    return NULL;

    //If only the string passed is NULL and the copy still has data, work with it.
    else
    {
        str=temp;
    }

    int chars=0, len = strlen(tokens), flag=0;
    
    //Run the loop till we find a token or our copy is fully parsed.
    while(*temp)
    {
        for(int i=0;i<len;i++)
        {
            if(*temp==tokens[i])
            {
                if(chars==0)
                {
                    flag=1;
                    str++;
                }
                else
                {
                    temp++;
                    str[chars]='\0';
                    return str;
                }
            }
        }
        if(flag==0)
            chars++;
        temp++;
        flag=0;
    }
    temp=NULL;
    str[chars]='\0';
    return str;
}