40 lines
1.2 KiB
C++
40 lines
1.2 KiB
C++
#include "doubly-linked-list.h"
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using namespace seq;
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// return the size (number of items in the doubly linked list)
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size_t DoublyLinkedList::size() const
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{
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size_t count = 0;
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for(DoublyLinkedListNode* n = this->head; n != nullptr; n = n->get_next()) count++;
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return count;
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}
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// add an item at the end of the list
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void DoublyLinkedList::enqueue(int value)
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{
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DoublyLinkedListNode* new_node = new DoublyLinkedListNode;
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new_node->set_item(value);
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if(this->empty()) this->head = new_node;
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else
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{
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this->tail->set_next(new_node);
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new_node->set_prev(this->tail); /** attachment in the doubly linked list goes both ways **/
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}
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this->tail = new_node;
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}
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// remove the head node and item
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int DoublyLinkedList::dequeue()
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{
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if(this->empty()) return 0; // nothing there to remove
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DoublyLinkedListNode* successor = this->head->get_next();
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if(successor) successor->set_prev(nullptr); /** we must detach the previous head node from its successor **/
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int outgoing = this->head->item;
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delete this->head;
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this->head = successor; // successor of the previous head is the new head
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if(this->head == nullptr) this->tail = nullptr; // catch special case: the list is now empty
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return outgoing;
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} |