Linked Lists. Lecture 16 Sections Robb T. Koether. Hampden-Sydney College. Wed, Feb 22, PDF Free Download

Linked Lists Lecture 16 Sections 17.1-17.3 Robb T. Koether Hampden-Sydney College Wed, Feb 22, 2017 Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 1 / 24

1 Linked Lists 2 The LinkedListNode Class 3 The LinkedList Class 4 Random Access vs. Sequential Access 5 Assignment Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 2 / 24

Outline 1 Linked Lists 2 The LinkedListNode Class 3 The LinkedList Class 4 Random Access vs. Sequential Access 5 Assignment Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 3 / 24

Linked Lists In a linked list, each node is allocated dynamically when the element is added to the list and deallocated dynamically when it is removed from the list. A linked list always uses exactly the amount of memory it needs. A linked list is more efficient than an array list in some ways and less efficient in others. The name of the linked list class is LinkedList. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 4 / 24

Linked Lists a 0 a 1 a 2... a n - 1 The abstract concept Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 5 / 24

Linked Lists a 0 a 1 a 2... a n - 1 The linked implementation Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 5 / 24

The LinkedListNode Class We create a separate class, LinkedListNode, as a data type that stores a single element of a linked list. Each LinkedListNode contains a data item and a pointer that links it to the next node. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 7 / 24

LinkedListNode Data Members LinkedListNode Data Members T m_value; LinkedListNode* m_next; m_value The element a i. m_next A pointer to the node containing the element a i+1 or NULL if a i is the last element. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 8 / 24

LinkedListNode Member Functions LinkedListNode Public Member Functions T value() const; T& value(); LinkedListNode* next(); T value() Returns a copy of the data member of the node (r-value). T& value(); Returns a reference to the data member of the node (l-value). next(); Returns a copy of the pointer to the next node. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 9 / 24

LinkedListNode Member Functions LinkedListNode Private Member Functions LinkedListNode(const T& val = T()); LinkedListNode(T&); Constructs a linked list node containing the specified value. It can be invoked only by friend classes. The only friend class (for now) will be the LinkedList class. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 10 / 24

LinkedListNode Destructor LinkedListNode Destructor ~LinkedListNode(); What should the LinkedListNode destructor do? Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 11 / 24

The LinkedListNode Class The LinkedListNode Class The header file linkedlistnode.h. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 12 / 24

The LinkedList Class LinkedList Data Members int m_size; LinkedListNode* m_head; m_size The number of elements in the list. m_head A pointer to the first node (which contains the first element). Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 14 / 24

The LinkedListNode Class m_size m_head m_value m_next m_value m_next m_value m_next LinkedList LinkedListNode LinkedListNode LinkedListNode Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 15 / 24

Validity Requirements of a Linked List The linked list structure is valid provided m_size >= 0. If m_size == 0, then m_head == NULL. If m_size > 0, then m_head!= NULL. For every i from 0 to m_size - 2, in node i, m_next!= NULL. In node m_size - 1, m_next == NULL. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 16 / 24

Random Access vs. Sequential Access A linked list allows sequential access, but not random access. To find the list element in position n, we must begin at the head of the list and move sequentially through positions 1, 2,..., n 1 before reaching position n. An array allows random, or direct, access. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 18 / 24

Random Access vs. Sequential Access Sequential access is much slower than random access if the list elements are accessed randomly. However, sequential access may be faster than random access if the list elements are accessed sequentially. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 19 / 24

The Technique of Chasing Pointers Chasing Pointers LinkedListNode* node = m_head; for (int i = 0; i < pos; i++) node = node->m_next; Technique of chasing pointers to locate position pos. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 20 / 24

Random Access vs. Sequential Access Random Access vs. Sequential Access for (int i = 0; i < list.size(); i++) list[i] = 0; How would the performance of the above for loop differ between the ArrayList and LinkedList implementations? Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 21 / 24

The LinkedList Class The LinkedList Class linkedlistnode.h. linkedlist.h. ListTest.cpp. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 22 / 24

Assignment Assignment Read Sections 17.1-17.3. Robb T. Koether (Hampden-Sydney College) Linked Lists Wed, Feb 22, 2017 24 / 24

Linked Lists. Lecture 16 Sections Robb T. Koether. Hampden-Sydney College. Wed, Feb 22, 2017