LeetCode Topic 2-Determine whether there is a ring in a given linked list

bool hasCycle(ListNode *head) 
{
    auto walker = head;
    auto runner = head;
    while(runner && runner->next)
    {
        walker = walker->next;
        runner = runner->next->next;
        if(walker == runner)
           return true;
    }

    return false;
}