So what's next?

1. So what's next? Introduction to data structures • Two Perspectives: • Abstract description (capabilities) • Implementation(s) • For structures: • Stack • Queue • Deque (maybe)

2. Clicker quiz12/3/13 CSE 1102 Fall 2013

3. The country with the red star on it is: • Canada • Sweden • Latvia • Finland • None of the above

4. Suppose I have a stack s that can store Strings, and I execute the following statements starting with an empty stack: • s.push("Finland"); • s.push("is"); • s.push("my"); • String w = s.peek(); • String x =s.pop(); • s.push("home"); • String y = s.pop(); • String z = s.pop(); • What is the value of z? • "Finland" • "is" • "my" • "home" • None of the above

5. Suppose I have a queue q that can store Strings, and I execute the following statements starting with an empty queue: • q.enqueue("Sweden"); • q.enqueue("is"); • q.enqueue("my"); • String w = q.dequeue(); • String x = q.peek(); • q.enqueue("neighbor"); • String y = q.dequeue(); • String z = q.dequeue(); • What is the value of z? • "Sweden" • "is" • "my" • "neighbor" • None of the above

6. Clicker questions and stuff12/3/13 CSE 1102 Fall 2013

7. Abstract Data Types (1970s) Description of a data structure that includes only its operations, not its implementation In Java, ADTs are best modeled by interfaces

8. Example ADT: Stack Operations: push(element) – adds element to "top" of the stack pop – returns the top element of the stack, which is removed from the stack peek – returns the top element of the stack without changing the stack isEmpty – returns true if stack is empty, false otherwise

9. Stack intuitions examples in the world uses in computing

10. Suppose I have a stack S that can store Strings, and I execute the following statements starting with an empty stack: • S.push("Iceland"); • S.push("is"); • String w = S.peek(); • String x =S.pop(); • S.push("cool"); • String y = S.pop(); • boolean z = S.isEmpty(); • What is the value of z? • "Iceland" • "cool" • true • false • None of the above

11. Example ADT: Queue Operations: enqueue(element) – adds element to "back" of the queue dequeue – returns the "front" element of the queue, which is removed from the queue front – returns the front element of the queue without changing the queue isEmpty – returns true if queue is empty, false otherwise

12. Queue intuitions examples in the world uses in computing

13. Suppose I have a queue q that can store Strings, and I execute the following statements starting with an empty queue: • q.enqueue("Sweden"); • q.enqueue("is"); • q.enqueue("my"); • String w = q.dequeue(); • String x = q.peek(); • q.enqueue("neighbor"); • String y = q.dequeue(); • String z = q.dequeue(); • What is the value of z? • "Sweden" • "is" • "my" • "neighbor" • None of the above

14. Suppose we have a class that acts as a Holder for Colors: public class ColorHolder { private Color _myColor; public ColorHolder(Color color) { _myColor = color; } public Color getValue(){ return _myColor; } public void setColor (Color col) { _myColor = col; } } It might be useful to have a more general version, that could hold anything. Quick Topic 1: Generics

15. Java allows us to define a class generically, with type declared at instantiation time: public class Holder<ValType> { private ValType _myValue; public Holder(ValType value) { _myValue = value; } public ValType getValue(){ return _myValue; } public void setValue (ValType value) { _myValue = value; } } To use this class, you need to declare and instantiate object with actual type: Holder<Color> currentColor; currentColor = new Holder<Color>(Color.red); More examples in Chapter 14!

16. Example: Node class holds an element of some type, plus another Node of the same sort. public class Node<ValType> { private ValType _myValue; private Node<ValType> _next public Node(ValType value) { _myValue = value; _next = null; } public ValType getValue(){ return _myValue; } public void setValue (ValType value) { _myValue = value; } public Node<ValType> getNext(){ return _next; } } Since _next is a Node of the same sort, we can chain instances of these together.

17. Suppose we want to diagram a set of instances and their relationships Answer: object (or instance) diagram Quick Topic 2: Object Diagrams For example, a sequence of two Nodes whose elements are Cars

18. "syntax"

19. Topic 3: Are you on this list? Bidhan Adhikari Devin Delaney Erming Gao Christopher Lawrence Jeffrey Metter Jonathan Rarey

20. ADT: defined by capabilities In Java: a natural fit to Interfaces, e.g. public interface StackADT<ElementType>{ void push(ElementType t); ElementType pop(); ElementType peek(); boolean isEmpty(); }

21. So let's use Nodes to implement a Stack One instance variable, _top, which refers to a Node Stack<Car> fred = new Stack<Car>(); // create empty Stack // now add some stuff fred.push(new Car(Color.RED)); fred.push(new Car(Color.BLUE));

22. So let's use Nodes to implement a Stack ctd. One instance variable, _top, which refers to a Node // now pop something Car ethyl = fred.pop(); // what actually happens is this

23. So let's use Nodes to implement a Stack public class Stack<ElType> implements StackADT<ElType>{ private Node<EiType> _top; public Stack() { _top = null; } public void push(EiType value) { Node<EiType> nodeToPush = new Node<EiType>(value); nodeToPush.setNext(_top); _top = nodeToPush; } public EiType pop() { EiType retVal = _top.getValue(); _top = _top.getNext(); return retVal; } public boolean isEmpty(){ return _top == null; } }