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Published byCrystal Gumbel Modified over 2 years ago

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The implementation of this class is testable on the AP CS AB exam. Stacks are last in first out. LIFO. A stack is a sequence of items of the same type. These items can only be added and removed at one end. Stack operations are either push or pop

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boolean isEmpty() Are there any elements in the stack? E push(E item) Add or push item onto to the stack. Returns the item. E pop() Return and Remove or pop last element pushed from the stack. EmptyStackLocation is thrown if empty. E peek() Return last element pushed from the stack. EmptyStackLocation is thrown if empty.

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Expressions within other expressions Methods that call other methods Traversing directories and subdirectories

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This interface is testable on the AB exam. Queues are first in first out. FIFO. A queue is a line of items of the same type. These items can only be added and removed at one end. Stack operations are either add or remove

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boolean isEmpty() Are there any elements in the queue? boolean add(E item) Put an element into the queue. E remove() Returns first element in the queue. NoSuchElement is thrown if the queue is empty. E peek() Returns the first element in the queue. Returns null if empty.

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Going back to the beginning and retracing steps. Simulating lines.

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Queue with a priority field. Elements in a priority queue must implement Comparable. Does not allow insertion of null elements. A NullPointerException is thrown if null. Priority Queues allow for: Rapid insertion of elements that arrive in arbitrary order. Rapid retrieval of the element with highest priority.

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A database of patients awaiting liver transplants, where the sickest patients have the highest priority Scheduling events. Events are generated in random order and each event has a time stamp denoting when the event will occur. The scheduler retrieves the events in the order they will occur.

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AlgorithmStackQueuePriority Queue InsertO(1) O(log n) RemoveO(1) O(log n) PeekO(1)

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The implementation of this class is testable on the AP CS AB exam. A binary tree is a finite set of elements that is either empty or contains a single element called the root. Each node in the tree has a Left and Right.

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Root Node Leaf Children Parent Descendant Ancestor Depth Level of a node Level of a tree Height Balanced Tree Perfect Binary Tree Complete Binary Tree

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A balanced binary tree is where the depth of all the leaves differs by at most 1. ABDEHCFG

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A perfect binary tree is a full binary tree in which all leaves are at the same depth or same level. ABDECFG

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ABDECF A complete binary tree is either perfect or perfect through the next- to-last level, with leaves as far left as possible in the last level.

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public class TreeNode { private Object value; private TreeNode left, right; public TreeNode(Object initValue); public TreeNode(Object initValue, TreeNode initLeft, TreeNode initRight); public Object getValue(); public TreeNode getLeft(); public TreeNode getRight(); public void setValue(Object theNewValue); public void setLeft(TreeNode theNewLeft); public void setRight(TreeNode theNewRight); }

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public abstract class BinaryTree { private TreeNode root; public BinaryTree() { root = null; } public TreeNode getRoot(); public void setRoot(TreeNode theNewNode); public boolean isEmpty() { return root == null; } public abstract void insert(Comparable item); public abstract TreeNode find(Comparable key); }

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The implementation of this class is testable on the AP CS AB exam. A binary search tree is a binary tree that stores elements in an ordered way that makes it efficient to find a given element and easy to access the elements in sorted order.

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public class BinarySearchTree extends BinaryTree { public void insert(Comparable item) { if(getRoot() == null) { setRoot(new TreeNode(item)); } else { TreeNode p = null, q = getRoot(); while(g != null) { p = q; if(item.compareTo(p.getValue()) < 0) { q = p.getLeft(); } else { q = p.getRight(); } if(item.compareTo(p.getValue()) < 0) { p.setLeft(new TreeNode(item)); } else { p.setRight(new TreeNode(item)); }

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public TreeNode find(Comparable key) { TreeNode p = getRoot(); while(p != null && key.compareTo(p.getValue()) != 0) { if(key.compareTo(p.getValue()) < 0) { p = p.getLeft(); } else { p = p.getRight(); } return p; }

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ABC In order BAC Preorder ABC Post order BCA In order Left-Root-Right Preorder Root-Left-Right Post order Left-Right-Root

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public void postorder() { doPostOrder(root); } private void doPostOrder(TreeNode t) { if(t != null) { doPostOrder(t.getLeft()); doPostOrder(t.getRight()); System.out.println(t.getValue()); }

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*-83+42 (8-3) * (4 + 2) *-83+42 83-42+*

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OperationBalanced BSTUnbalanced BST Insert 1 elementO(log n)O(n) Insert n into empty BSTO(n log n)O(n^3) Search for keyO(log n)O(n) Traverse TreeO(n)

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