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Data Structures and Applications. Hao Jiang Computer Science Department Boston College. Linked List. head. 1. 2. 3. 4. null. … Node head; Node v1 = new Node(1); Node v2 = new Node(2); Node v3 = new Node(3); Node v4 = new Node(4); head = v1; v1.next = v2; v2.next = v3;
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Data Structures and Applications Hao Jiang Computer Science Department Boston College
Linked List head 1 2 3 4 null … Node head; Node v1 = new Node(1); Node v2 = new Node(2); Node v3 = new Node(3); Node v4 = new Node(4); head = v1; v1.next = v2; v2.next = v3; v3.next = v4; v4.next = null; class Node { public int d; public Node next; public Node(int d) { this.d = d; next = null; } }
Some Properties head 1 2 3 4 null A list is dynamic: the length of a list is determined in the runtime. Some operations such as insertion and deletion are cheaper than the data structure array.
Insert head 1 2 3 4 null 100 Insert a new node at position 1.
Insert in the Front head 1 2 3 4 null 100 Insert a new node at position 0.
Insert at the End head 1 2 3 4 100 null Insert a new node at the end.
Delete head 1 2 3 4 null Delete a new node at position 1.
Delete from the Front head 1 2 3 4 null Delete a node at position 0.
Delete the Last Node head 1 2 3 4 null null Delete the last node in the list.
A List of Objects head obj1 obj2 obj3 obj4 null class Node { public Object d; public Node next; public Node(Object d) { this.d = d; next = null; } }
A More Accurate Illustration obj1 obj2 obj3 obj4 head null A list of objects.
List Class public class List { private Node head; public List() { head = null; } public boolean isEmpty() { return (head == null); } public int length(Node h) { if (h == null) return 0; return 1 + length(h.next); } public int length() { return length(head); } … public void append() {…} public void insert(int n, Object d) {…} public Object delete(int n) {…} public void print() {…} … }
Queue • A queue is a first-in-first-out linear data structure. • It supports two operations: • void enQueue(Object d) • Object deQueue() Data Out Data In
Stack • A stack is a first-in-last-out linear data structure. • It supports two operations: • void push(Object d) • Object pop() top of the stack bottom of the stack
Queue based on List public class Queue { private List list; public Queue() { list = new List(); } public void enQueue(Object d) { list.append(d); } public Object deQueue() { Object t = list.getHead(); list.delete(0); return t.d; } }
Stack based on List public class Stack { private List list; public Stack() { list = new List(); } public void push(Object d) { list.insert(0, d); } public Object pop() { Node t = list.getHead(); list.delete(0); return t.d; } }
Simulation • Application of the Queue Gas Station car1 car2 car3 car4 Top of the line End of the line How long does everyone have to wait? How long can the line be?
Language Parser • We can use stacks to make language parsers. • ( ( 1 + 2 ) / 3 ) = ? 2 1 + 3 ) ( ( 1 + 2 3 3 / 1 The result is 1. ) / 3