5 linked list tủ tài liệu bách khoa

Trần Thị Thanh Nga ngattt@hcmuaf.edu.vn Khoa Công nghệ thông tin, ĐH Nông Lâm HCM Linked List Arrays  Advantages:  Arrays are nice and simple for storing things in a certain order  Drawbacks  Arrays are not very adaptable, since we have to fix the size N of an array in advance,  Have to use integer indices to access its contents Linked List Linked List  A linked list, is a collection of nodes that together form a linear ordering  Each node is an object that stores a reference to an element and a reference, called next, to another node  The next reference inside a node can be viewed as a link or pointer to another node  The first of a linked list usually are called the head of the list Linked List Linked List  A singly linked list keeps its elements in a certain order This order is determined by the chain of next links going from each node to its successor in the list  A singly linked list does not have a predetermined fixed size, and uses space proportional to the number of its elements  Do not keep track of any index numbers for the nodes in a linked list Linked List Type of List  Depending on the way in which the links are used to maintain adjacency, several different types of linked lists are possible  Linear singly-linked list (or simply linear list)  Circular linked list  Doubly linked list Linked List Singly linked list  Linear singly-linked list (or simply linear list)  Advantages: • Simple implementation, • Efficient, constant time O(1) insertion and removal operation Linked List Circular linked list  The pointer from the last element in the list points back to the first element Linked List Doubly Linked List  Pointers exist between adjacent nodes in both directions • The list can be traversed either forward or backward • Usually two pointers are maintained to keep track of the list, header and trailer • Advantage: faster (bi-directional) traversal • But, more control data (links) stored Linked List Implement a Singly Linked List  To implement a singly linked list, we define a Node class which specifies the type of objects stored at the nodes of the list  Given the Node class, we can define a class, LinkedList, defining the actual linked list  This class keeps a reference to the head node and a variable counting the total number of nodes Linked List Node class public class Node { private T data; private Node next; public Node(T data, Node next) { this.data = data; this.next = next; } public T getData() { return data; } public void setData(T data) { this.data = data; } Linked List LinkedList class public class LinkedList { protected Node head; public LinkedList() { head = null; } } Linked List Traversing  Start with the head and access each node until you reach null Linked List Traversing Node tmp = head; while(tmp != null) tmp = tmp.next; Linked List Adding an item at the head  We can easily insert an element at the head of the list The main idea is:  Create a new node, set its next link to refer to head  Set head to point to the new node Linked List Adding an item at the head public void addFirst(T item) { Node newNode = new Node(item, head); head = newNode; } Linked List Adding an Element at the end  Create a new node newNode, assign its next reference to point to the null object (1 statement)  Traversing the list and stop at the last node (2 statements)  Set the next reference of the last node to point to newNode (1 statement) Linked List Adding an Element at the end public void addLast(T item) { if (head == null) addFirst(item); else { Node newNode = new Node(item, null); Node tmp = head; while (tmp.next != null) tmp = tmp.next; tmp.next = newNode; } } Linked List Inserting after a node  Finding a node containing "key" and insert a new node after it Linked List Inserting after a node public void insertAfter(T key, T toInsert) { Node tmp = head; while(tmp != null && !tmp.getData().equals(key)) tmp = tmp.next; if(tmp != null) tmp.next = new Node(toInsert, tmp.next); } Linked List Inserting before a node  Finding a node containing "key" and insert a new node before it Linked List Inserting before a node public void insertBefore(T key, T toInsert) { if(head == null) return; if(head.getData().equals(key)) { addFirst(toInsert); return; } Node prev = null; Node cur = head; while(cur != null && !cur.getData().equals(key)) { prev = cur; cur = cur.next; } if(cur != null) prev.next = new Node(toInsert, cur); Linked List } Deletion  Find a node containing "key" and delete it Linked List Deletion public void remove(T key) { if(head == null) throw new RuntimeException("cannot delete"); if( head.getData().equals(key) ) { head = head.next; return; } Node cur = head; Node prev = null; Linked List Deletion while(cur != null && !cur.getData().equals(key) ) { prev = cur; cur = cur.next; } if(cur == null) throw new RuntimeException("cannot delete"); //delete cur node prev.next = cur.next; } Linked List Question? Linked List ... singly -linked list (or simply linear list)  Circular linked list  Doubly linked list Linked List Singly linked list  Linear singly -linked list (or simply linear list)  Advantages: • Simple implementation,... linked list Linked List Type of List  Depending on the way in which the links are used to maintain adjacency, several different types of linked lists are possible  Linear singly -linked list (or... link or pointer to another node  The first of a linked list usually are called the head of the list Linked List Linked List  A singly linked list keeps its elements in a certain order This order