Chapter 4. Linked Lists. M hiwa ahmad aziz

Transcription

1 . Chapter 4 Linked Lists M hiwa ahmad aziz 1

2 Array (lists) You can create an array to store objects. But, once the array is created, its size is fixed. data structure : Lecturer ( ( m hiwa ahmad aziz) 2

3 Advantages and Limitation of array Advantages No need to declare large number of variables individually. Variables are not scattered in memory, they are stored in contiguous memory. Ease the handling of large variables in every data type Limitation Rigid structure. Can be hard to insert/remove elements. Cannot be dynamically resized in most languages. Memory loss. data structure : Lecturer ( ( m hiwa ahmad aziz) 3

4 Problems of insert array data structure : Lecturer ( ( m hiwa ahmad aziz) 4

5 Linked list Linked list data structure is dynamic, with a linear arrangement of objects placed. Unlike arrays, where access to data by the index, the linked list is with a pointer There are two types of One-way linked, tow-way linked. data pointer 5

6 Compare linked list and Array 1) Access to array elements of the linked list is faster, because the index is determined each array. 2) Insert and remove the linked list to provide easier, because no need for physical movement memory elements. 3) There is not possibility of a binary search in the linked list data structure : Lecturer ( ( m hiwa ahmad aziz) 6

7 One-way linked One-way linked list is a list that each element is kept only address the next element. Each node in the linked list consists of two parts data and pointer (address). Must know the pointer to the first element of the list (called start or head ). Last element points to NULL. class Node{ Object data; Node next; Node(Object d){ data=d; }//end node constructor } 7

8 Inserting to the Front head 1. Allocate a new node 2. Insert new element 3. Have new node point to old head 4. Update head to point to new node public void insertfirst (Object item) { p=new Node(item); p.next=head; head=p; count++; } 8

9 Inserting to the after 1. Allocate a new node 2. Insert new element 3. Go to the node that should follow the one to add q 4. Have that node point to the new node 5. Have new node point to node next node to the found node public void insertafter(object newitem,object key){ p=find(key); if(p==null) System.out.println(key+" key is not found"); else { Node q=new Node(newitem); q.next=p.next; p.next=q; count++; }//end if } 9

10 Display and find. Find node public Node find(object key){ p=head; while(p!=null){ if(p.data==key) return p; p=p.next; }//end while return null; }.... Display public void display(){ p=head; while(p!=null){ System.out.print(p.data+" ---> "); p=p.next; }//end while System.out.println(p); }//end display data structure : Lecturer ( ( m hiwa ahmad aziz) 10

11 Delete head node head public Object deletefirst(){ if(head == null){ System.out.println("List is Empty: no deletion"); return null; }//end if Node tmp=head; head=tmp.next; count--; return tmp.data; }//end deletefirst 11

12 Delete middle node public Object deleteafter(object key) { p=find(key); if(p.next==null){ System.out.println(" no deletion"); return null; } else{ Node d = p.next; p.next = d.next; count--; return d.data; } }//end deleteafter data structure : Lecturer ( ( m hiwa ahmad aziz) 12

13 Several applications of linked list Several applications of linked list 1) View polynomials as the linked list 2) Stack implementation with linked list 3) Queue implementation with linked list data structure : Lecturer ( ( m hiwa ahmad aziz) 13

14 View polynomials as the linked list Of linked lists can be used to implement polynomials. In this case, each node will be consists of three parts. Coefficient power pointer Suppose you have two polynomials. And want to keep them together 7x^5 + 3x^3 6x^2+ 4 5x^6-4x^5+2x^4+2x^2-x When the two polynomials the following conditions exist: 1) binomial that we face are isotonic coefficients are added together. Follow them put together. 2) One of the more such sentences power selected and be left behind. 14

15 Linked stack Using a linked list to implement Linked stack. As you know, the stack entry and exit data on the one hand done. top 0 Insert in stack E Delete in stack 15

16 Linked queues. As you know in the input Queue on the one hand, and exit on other side The reason we need two pointers to name the rear and front. front rear 0 16

17 Doubly link list In doubly link list each node p has references to both the node p.next that follows it and the node p.prev that precedes it. 17

18 Insert Doubly link list insert after the right node with address q For insert after we need to change 4 pointer

19 Delete Doubly link list Following method deleted p node with certain address 1 2 For delete we need to change 2 pointer 19

20 Circuit Doubly link list In the circuit link list end node implicit to start node so start node implicit to end node and if we have every address of node can access all nodes Circuit Doubly link list 20

21 Move from head displayforward and displaybackward Move from tail

22 Find and length