WGU C949 Data Types STUDY GUIDE with correct answers.

Array A data structure that stores an ordered list of items, with each item is directly accessible by a positional index. Linked List A data structure that stores ordered list of items in nodes, where each node stores data and has a pointer to the next node. Bianary Search Tree A data structure in which each node stores data and has up to two children, known as a left child and a right child. Hash Table A data structure that stores unordered items by mapping (or hashing) each item to a location in an array (or vector). Abstract Data Type (ADT) A data type described by predefined user operations, such as "insert data at rear," without indicating how each operation is implemented. List An ADT for holding ordered data. Dups ok Sequence type: A mutable container with ordered elements. Underlying data structures: Array, linked list Array in Java generic class that supports different data types. declared as follows, where T is the data type. Tuple Sequence type: An immutable container with ordered elements. Stack An ADT in which items are only inserted on or removed from the top of a stack. *Last-in First-Out Underlying data structures: Linked list Push(stack, x), pop(stack), peek(stack), IsEmpty(stack), GetLength(stack) *Pop & peek should not be used on a empty stack. Stack operations Example starting with stack: 99, 77 (top is 99). Push(stack, x) Inserts x on top of stack Push(stack, 44). Stack: 44, 99, 77 Pop(stack) Returns and removes item at top of stack Pop(stack) returns: 99. Stack: 77 Peek(stack) Returns but does not remove item at top of stack Peek(stack) returns 99. Stack still: 99, 77 IsEmpty(stack) Returns true if stack has no items IsEmpty(stack) returns false. GetLength(stack) Returns the number of items in the stack GetLength(stack) returns 2. Queue An ADT in which items are inserted at the end of the queue and removed from the front of the queue. *first-in first-out ADT. Underlying data structures: Linked list, Array, Vector The Queue class' push() method uses the LinkedList append() method to insert elements in a queue. Both the Stack and Queue pop() methods operate exactly the same by removing the head element and returning the removed element. Linked List A linear data structure, much like an array, that consists of nodes, where each node contains data as well as a link to the next node, but that does not use contiguous memory. Head and tail node The LinkedList class implements the list data structure and contains two data members, head and tail, which are assigned to nodes once the list is populated. Initially the list has no nodes, so both data members are initially assigned with None. If the node has no next node, the next data member is assigned with None, the Python term signifying the absence of a value. Deque Short for double-ended queue- an ADT in which items can be inserted and removed at both the front and back. Underlying data structures: Linked list Bag An ADT for storing items in which the order does not matter and duplicate items are allowed. Underlying data structures: Linked list, Array Set An ADT for a collection of distinct items. (no dups!) Underlying data structures: Binary search tree, Hash table Priority queue A queue where each item has a priority, and items with higher priority are closer to the front of the queue than items with lower priority. Dups ok Underlying data structures: Heap *In addition to push and pop, a priority queue usually supports peeking and length querying. A peek operation returns the highest priority item, without removing the item from the front of the queue. Pop returns front or head item which is top priority item Dictionary (Map) A dictionary is an ADT that associates (or maps) keys with values. Underlying data structures: Binary search tree, Hash table Dictionary key characteristic They are unique and immutable. Dictionary method D1[key].remove(value) () returns a view object that yields (key, value) tuples. () returns a view object that yields dictionary keys. s() returns a view object that yields dictionary values.