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Chapter 17 Linked List Saurav Karmakar Spring 2007

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LISTS Easiest implementation of LIST --- ARRAY :: has Disadvantages. 1) To insert an item at the beginning or middle of an array sliding lots of items over one place to make room :: ~ O(n) 2) Arrays have a fixed length :: can't be changed. Adding items to a list Allocation a whole new array if the array containing LIST is full and then move all the items from the old array to the new one.

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Linked List Consists of connected, dynamically allocated nodes. A linked list is made up of "nodes". Each node has two components: an item, and a reference to the next node in the list.

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Comparison with Array 1.Arrays contiguous direct access of elements insertion / deletion difficult 2.Linked Lists noncontiguous must scan for element insertion /deletion easy 1.Arrays contiguous direct access of elements insertion / deletion difficult 2.Linked Lists noncontiguous must scan for element insertion /deletion easy arrayname

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for (int i = 0; i < length; i++) cout<< a[i]; for (ListNode p = theList.first; p != null; p = p.next) cout<< p.data ; for (int i = 0; i < length; i++) cout<< a[i]; for (ListNode p = theList.first; p != null; p = p.next) cout<< p.data ; a Iterating through the data structure

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class ListNode { Object data; ListNode* next; } At any point, we can add a new last item x by doing this: Last->next = new ListNode(); last = last->next; Last->data = x; Last->next = null; A0A1A2 firstlast Adding an element

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class ListNode { Object data; ListNode* next; } At any point, we can add a new last item x by doing this: Last->next = new ListNode(); last = last->next; Last->data = x; Last->next = null; A0A1A2 firstlast

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class ListNode { Object data; ListNode* next; } At any point, we can add a new last item x by doing this: last->next = new ListNode(); last = last->next; Last->data = x; Last->next = null; A0A1A2 firstlast

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class ListNode { Object data; ListNode* next; } At any point, we can add a new last item x by doing this: last->next = new ListNode(); last = last->next; Last->data = x; Last->next = null; A0A1A2x firstlast

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class ListNode { Object data; ListNode* next; } At any point, we can add a new last item x by doing this: Last->next = new ListNode(); last = last->next; Last->data = x; Last->next = null; A0A1A2x firstlast

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class ListNode { Object element; ListNode* next; } At any point, we can insert a new item x by doing this: tmp = new ListNode(); Tmp->element = x; Tmp->next = current->next; Current->next = tmp; last Inserting an element A0A1A2 first current

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class ListNode { Object element; ListNode* next; } At any point, we can insert a new item x by doing this: tmp = new ListNode(); Tmp->element = x; Tmp->next = current->next; Current->next = tmp; Inserting an element A0A1A2 first last current tmp

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class ListNode { Object element; ListNode* next; } At any point, we can insert a new item x by doing this: tmp = new ListNode(); Tmp->element = x; Tmp->next = current->next; Current->next = tmp; Inserting an element A0A1A2 first last current x tmp

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class ListNode { Object element; ListNode* next; } At any point, we can add a new last item x by doing this: tmp = new ListNode(); Tmp->element = x; Tmp->next = current->next; current->next = tmp; Inserting an element A0A1A2 first last current x tmp

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class ListNode { Object element; ListNode* next; } At any point, we can add a new last item x by doing this: tmp = new ListNode(); Tmp->element = x; Tmp->next = current->next; Current->next = tmp; Inserting an element A0A1A2 first last current x tmp

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Simplified version Current->next = new ListNode(x, current->next) tmp = new ListNode(); Current->next = tmp; Tmp->next = current->next; Tmp->element = x;

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class ListNode { Object element; ListNode* next; } Current->next = current->next->next; Deleting an element A0A1A2 current last

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class ListNode { Object element; ListNode* next; } Current->next = current->next->next; Memory leak! Deleting an element A0A1A2 last current

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Delete a Node Node *deletedNode = current->next; Current- >next = current->next->next; Delete deletedNode;

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Length Function The Length function takes a linked list and computes the number of elements in the list. /*Given a linked list head pointer, compute and return the number of nodes in the list.*/ int Length(struct node* head) { struct node* current = head; int count = 0; while (current != NULL) { count++; current = current->next; } return count; }

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abc header Header nodes allow us to avoid special cases [in the code] such as insertion of the first element and removal of the last element. The header node holds no data but serves to satisfy the requirement that every node have a previous node. Not necessarily a standard implementation. Header node

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abc head tail class DoubleListNode { Object element; ListNode* next; ListNode* prev; } class DoubleListNode { Object element; ListNode* next; ListNode* prev; } A doubly linked list allows bidirectional traversal by storing two pointers per node. Doubly Linked Lists

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head tail // constructor DoubleList() { head = new DoubleListNode (); tail = new DoubleListNode (); head->next = tail; tail->prev = head; } Empty Doubly Linked List

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newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode Inserting into a Doubly Linked List ac head tail current

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Inserting into a Doubly Linked List ac head tail newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode b current

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Inserting into a Doubly Linked List ac head tail newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode b current

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Inserting into a Doubly Linked List ac head tail newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode b current

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newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode Inserting into a Doubly Linked List ac head tail b current

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newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode Inserting into a Doubly Linked List ac head tail b current

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newNode = new DoublyLinkedListNode() newNode->prev = current; newNode->next = current->next; newNode->prev->next = newNode; newNode->next->prev = newNode; current = newNode Inserting into a Doubly Linked List ac head tail b current

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Circular Linked Lists abcd first

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Sorted Linked List A sorted link list is one in which items are in sorted order. The major difference from linked list is the insertion operation.

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