Can I destroy the structure of this linklist? It seems no restriction of that appears in the question

  • 0

    Link all nodes' next to head, thus if there is a circle, the pointer will walk to head again.

        bool hasCycle(ListNode *head)
        if(!head) return false;
        ListNode* p = head->next;
            if(p == head) return true;
            ListNode* q = p->next;
            p->next = head;
            p = q;
        return false;

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