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LAB#4 Overview Before we go to our lesson we must know about : 1. data structure . 2. Algorithms . data structure is an arrangement of data in a computer’s memory (or sometimes on a disk). Data structures include linked lists, arry , stacks, binary trees, and hash tables. Algorithms is manipulate the data in these structures in various ways, such as inserting a new data item, searching for a particular item, or sorting the items. 2 Overview of Data Structures A data structure is an arrangement of data in a computer’s memory (or sometimes on a disk). Data structures include linked lists, stacks, binary trees, and hash tables. Overview of Algorithms Algorithms manipulate the data in these structures in various ways, such as inserting a new data item, searching for a particular item, or sorting the items. 3 Arrays: pluses and minuses + Fast element access. -- Impossible to resize. • Many applications require resizing! • Required size not always immediately available. • All of these problem in array we can fix it we linked list Linked Lists 4 Q: What is the meaning of this symbol -> It mean Accessing Class Members Through an object of the class using (.) Through a pointer to the class using (->) For example: Student S1; S1. setstnum(1234); Student *S1ptr; Or (*S1ptr).setstnum(1234); S1ptr-> setstnum(1234); Linked List : A B C 0 Tail Head • A linked list is a series of connected nodes. • Each node contains at least: – A piece of data (any type) – Pointer to the next node in the list • Head: pointer to the first node. • The last node points to NULL. node A data pointer Singly Linked List : • We use two classes: Node and List o Declare IntSLLNode class for the nodes class IntSLLNode { public: IntSLLNode() { next = 0; } IntSLLNode(int i, IntSLLNode *ptr = 0) { info = i; next = ptr; } int info; IntSLLNode *next; }; Singly Linked List : o Declare IntSLList which contains : class IntSLList { public: IntSLList() {head = tail =0; } void AddToHead(int); void AddToTail(int); void DeleteFromHead(); void DeleteFromTail(); void DeleteNode(int); bool isInList(int) const; void DisplayList(); private: IntSLLNode *head, *tail; }; Inserting at the Head 1. Allocate a new node 2. Insert new element 3. Make new node point to old head 4. Update head to point to new node Linked Lists 9 Singly Linked List : o Declare IntSLList Class member function: 1- void AddToHead(int); void IntSLList::AddToHead(int el) { head = new IntSLLNode(el,head); if (tail == 0) tail = head; } Inserting at the Tail Allocate a new node Insert new element Have new node point to null Have old last node point to new node Update tail to point to new node .1 .2 .3 .4 .5 Linked Lists 11 Singly Linked List : o Declare IntLList Class member function: 2- void AddToTail(int); void IntSLList::AddToTail(int el) { if (tail != 0) // if list not empty; { tail->next = new IntSLLNode(el); tail = tail->next; } else head = tail = new IntSLLNode(el); } Removing at the Head 1. Update head to point to next node in the list 2. Allow garbage collector to reclaim the former first node Linked Lists 13 Singly Linked List : o Declare IntLList Class member function: 3- void DeleteFromHead(); void IntSLList::DeleteFromHead(){ if(head !=0) { IntSLLNode *tmp =head; if (head == tail) //if only one node in the list head = tail = 0; else head = head ->next; delete tmp;} } Removing at the Tail • Removing at the tail of a singly linked list cannot be efficient! • There is no constanttime way to update the tail to point to the previous node Linked Lists 15 Singly Linked List : 4- void DeleteFromTail(); void IntSLList::DeleteFromTail() {if(head != 0) {if (head == tail) //if only one node in the list {delete head; head=tail=0;} else { IntSLLNode *tmp; //find the predecessor of tail for(tmp=head; tmp->next != tail; tmp = tmp->next); delete tail; tail=tmp; tail->next=0;}} } Singly Linked List : o Declare IntLList Class member function: 5- int DeleteNode(int el); Singly Linked List : o Declare IntLList Class member function: 6- bool isInList(int) const; bool IntSLList:: isInList(int el) const { IntSLLNode *tmp; for (tmp=head; tmp != 0 && !(tmp->info == el); tmp = tmp->next); return tmp !=0; } Singly Linked List : o Declare IntSLList Class member function: 7- void DisplayList(); void IntSLList::DisplayList() {IntSLLNode *current; current = head; cout << "head = " << head << "\n"; while(current != 0) {cout << current->info << " " << current << "\n"; current=current->next;} cout << "tail = " << tail << "\n"; cout << "----------------------" << "\n";} Singly Linked List : • Using List : void main() {IntSLList myllist; myllist.AddToHead(50); myllist.AddToHead(90); myllist.AddToHead(60); myllist.AddToHead(68); myllist.DisplayList(); myllist.DeleteFromHead(); myllist.DeleteNode(60); if (myllist.isInList(60)== 0) cout<<"60 isn't in the list" << endl; cout<<"60 is in the list" << endl; myllist.DisplayList();} Doubly Linked List • A doubly linked list is often more convenient! • Nodes store: – element – link to the previous node – link to the next node prev next elem node • Special trailer and header nodes nodes/positions header trailer elements Linked Lists 22 Doubly Linked List : o Declare IntDLLNode which contains : class IntDLLNode{ public: IntDLLNode() {next=prev=0;} IntDLLNode(int el,IntDLLNode *n=0,IntDLLNode *p=0){ info = el; next=n; prev =p; } Int info; IntDLLNode *next, *prev; }; Doubly Linked List : o Declare IntDLList which contains : class IntDLList{ public: IntDLList(){ Head=tail=0;} void addToDLLTail(int el); void deleteFromDLLTail(); void IntDLList::DisplayFromHead(); protected: IntDLLNode *head ,*tail; }; Insertion • We visualize operation insertAfter(p, X), which returns position q p A B C p A q B C X p A q B Linked Lists X C 25 Insertion Algorithm Algorithm insertAfter(p,e): Create a new node v v.setElement(e) v.setPrev(p) {link v to its predecessor} v.setNext(p.getNext()) {link v to its successor} (p.getNext()).setPrev(v) {link p’s old successor to v} p.setNext(v) {link p to its new successor, v} return v {the position for the element e} Linked Lists 26 Doubly Linked List : o Declare IntDLList Class member function: 1- void addToDLLTail(int el); void IntDLList:: addToDLLTail(int el) {if (tail!=0){ tail=new IntDLLNode(el,0,tail); tail->prev->next=tail;} else head=tail=new IntDLLNode(el); } Deletion • We visualize remove(p), where p == last() A B C A B C p D p D A B Linked Lists C 28 Deletion Algorithm Algorithm remove(p): t = p.element {a temporary variable to hold the return value} (p.getPrev()).setNext(p.getNext()) {linking out p} (p.getNext()).setPrev(p.getPrev()) p.setPrev(null) {invalidating the position p} p.setNext(null) return t Linked Lists 29 Doubly Linked List : o Declare IntDLList Class member function: 2- void deleteFromDLLTail() void IntDLList:: deleteFromDLLTail() {if(tail !=0){ if(head==tail) { //if only one node in the list delete head; head = tail =0;} else { tail = tail->prev; delete tail->next; tail->next = 0;}}} Doubly Linked List : o Declare IntDLList Class member function: 2- void IntDLList::DisplayFromHead(); void IntDLList::DisplayFromHead() { IntDLLNode *current; for( current = head ; current != 0 ; current = current->next ) cout<<current->info<<endl; cout<<"--------------------------------"<<endl; } Evolution question • Create empty linked list and then add a new node with data 50 Answer of Evolution question