1. Week 3 - Wednesday

2.  What did we talk about last time?  Started linked lists

4. Bitmap Manipulator

6. Impromptu Student Lecture

7.  You are given a singly linked list  It may have a loop in it, that is, a node that points back to an earlier node in the list  If you try to visit every node in the list, you’ll be in an infinite loop  How can you see if there is a loop in a linked list?

9.  Let’s try a simple definition for a linked list: public class LinkedList { private static class Node { public int data; public Node next; } private Node head = null; … }

13.  Linked lists can be made circular such that the last node points back at the head node  This organization is good for situations in which we want to cycle through all of the nodes in the list repeatedly tail 23 47 58

14.  Insert at front (or back)  O(1)  Delete at front  O(1)  Delete at back costs O(n) unless we used doubly linked lists  Search  O(n)

15.  We can design linked lists with multiple pointers in some nodes  We want ½ of the nodes to have 1 pointer, ¼ of the nodes to have 2 pointers, 1/8 of the nodes to have 3 pointers… head 14 5 5 3 3 29 28 41 58 X X X

16.  If ordered, search is  O(log n)  Go to index is  O(log n)  Insert at end  O(log n)  Delete  Totally insane, at least O(n)  Trees end up being a better alternative

17.  We want to make items that are used frequently easy to get at  Several different approaches, mostly based on finding items repeatedly  Move to front: After finding an item, put it in the front  Transpose: After finding an item, move it up by one  Count: Keep the list ordered by how often you get a particular item (requires a counter in each node)  Ordering: Sort the list according to some feature of the data

20.  Generic linked list implementation  JCF List interface  ArrayList class  LinkedList class

21.  Keep reading Chapter 3  Keep working on Project 1  Due Friday, September 19 by 11:59pm  Finish Assignment 2  Due Friday by 11:59pm