【剑指offer】题53：正则表达式匹配

bool match_core(char* str,char * pattern)
{
    if (*str == ''&&*pattern == '')
    {
        return true;
    }
    if (*str != '' && *pattern == '') 
    {
        return false;
    }
    if (*(pattern+1)=='*')
    {
        if ((*pattern == *str)||(*pattern=='.'&&*str!=''))
        {
            return match_core(str + 1,pattern + 2)
                || match_core(str + 1,pattern)
                || match_core(str,pattern + 2);
        }
        else
        {
            return match_core(str,pattern + 2);
        }
    }
    if ((*str == *pattern) || (*pattern == '.'&&*str != ''))
    {
        return match_core(str + 1,pattern + 1);
    }
    return false;
}

bool match(char* str,char* pattern)
{
    if (str==NULL||pattern==NULL)
    {
        return false;
    }
    return match_core(str,pattern);
}