Course Review ICS 211 Cam Moore Information and

Course Review ICS 211 Cam Moore Information and Computer Sciences University of Hawaii, Manoa (1)

Java Concepts Objects vs. Primitives • References • Equality • Comparison Generic Types Collections • iterators (2)

Data Structures Arrays • Fixed size • System. array. Copy(src, src. Pos, dest. Pos, length) • Constant time access • Can have empty space (3)

Data Structures Lists /** An ordered collection. The user can access elements by their * integer index, and search for elements in the list. */ public interface List<E> extends Collection<E> { E get(int index); // returns object at given position E set(int index, E element); // sets element, returns old value int index. Of(Object o); // returns index of object in list E remove(int index); // removes object at the given position int size(); // returns number of elements in list boolean add(E element); // add element at the end of the list void add(int index, E element); // add element at given position } • Variable size • Linked and Array Implementations - Performance (4)

Data Structures Stacks /** A Stack represents a Last-In-First-Out (LIFO) stack of objects. */ public interface Stack<E> { boolean empty(); // returns true if the stack is empty E peek(); // looks at the top item of the stack w/o removing it. E pop(); // removes the top item in the stack, returning it. E push(E element); // pushes an item onto the top of the stack. } • Linked vs Array Implementation - Performance • Uses (5)

Pre, In, Post fix Notation Prefix Notation • Operator, Operand 1, Operand 2 • No operator precedence Infix Notation • Operand 1, Operator, Operand 2 • Has operator precedence and parentheses Postfix Notation • Operand 1, Operand 2, Operator • No operator precedence (6)

Data Structures Queues /**A collection designed for holding elements prior to processing. */ public interface Queue<E> extends Collection<E> { public boolean add(E e); // Inserts element to end of queue, throws exception public boolean offer(E e); // Inserts element to end of queue public E element(); // Retrieves, but doesn’t remove, the head of the queue public E peek(); // Retrieves, but doesn’t remove, the head or null public E poll(); // Retrieves and removes the head or null if queue is empty public E remove(); // Retrieves and removes the head of the queue public int size(); // Returns the number of elements in the queue. } • Add to the rear, remove from the front • Array vs Linked implementation - Performance • Uses (7)

Data Structures Trees • Terminology: - root, child, siblings, parent, height/depth, branch, leaf • Binary Trees - Full, Perfect, Complete - Traversals: pre order, in order, post order • Binary Search Trees (8) • Huffman Trees

Data Structures Heaps • Helper data structure • Parents are > or < children • Implemented in complete binary tree - left child = 2 * p + 1, right child = 2 * p + 2 - parent = (c – 1) / 2 - Add, reheap - Remove root, swap rightmost child, reheap (9)

Data Structures Hash tables • Goal constant time access to keyed value • Calculate index given key • Open Addressing vs chaining (10)

Recursion Problem solving technique if can solve problem else solve simpler problem and combine Data structure definition • Linked lists, trees Java Activation Stack (11)

Sorting Algorithms Quadratic • Implementation using an array • Selection - Best O(n 2), Ave O(n 2), Worst O(n 2) • Bubble - Best O(n), Ave O(n 2), Worst O(n 2) • Insertion - Best O(n), Ave O(n 2), Worst O(n 2) (12)

Sorting Algorithms n log n • Merge - Recursive, split then merge - O(n log n), O(n log n) • Heap - Insert to heap then remove - O(n log n), O(n log n) (13) • Quick - Recursive, Pick pivot then swap - O(n log n), O(n 2)