CMSC 132:
Object-Oriented Programming II
Linear Data Structures
Department of Computer Science
University of Maryland, College Park
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Linear Data Structures - Object-Oriented Programming II | CMSC 132, Study notes of Computer Science
Material Type: Notes; Class: OBJECT-ORIENTED PROG II; Subject: Computer Science; University: University of Maryland; Term: Unknown 1989;
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CMSC 132:
Object-Oriented Programming II
Linear Data Structures
Department of Computer Science
University of Maryland, College Park
Overview
Linear data structures
General properties
Implementations
Array Linked list
Restricted abstractions
Stack Queue
Linear Data Structures
Terminology
Head (first element in list)
no predecessor Tail (last element in list)
no successor
Operations
Add element Remove element Find element
Add & Remove Elements
Add an element
Where? At head (front) of list At tail (end) of list After a particular element
Remove an element
Remove first element Remove last element Remove a particular element (e.g., String “Happy”) What if “Happy” occurs more than once in list?
List Implementations
Two basic implementation techniques for lists
Store elements in an array Store as a linked list Place each element in a separate object (node) Node contains reference to other node(s) Link nodes together
Linked List
Properties
Elements in linked list are ordered Element has successor
State of List
Head Tail Cursor (current position) HeadTail Cursor
Linked Implementation
Advantages
Can efficiently insert / remove elements anywhere
Disadvantages
Cannot efficiently access element at any position Need to traverse list to find element Less efficient use of space 1-2 additional references per element
Efficiency of Operations
Array
Insertion / deletion = O( n
Indexing = O(
Linked list
Insertion / deletion = O(
Indexing = O( n
Linked List – Insert (After Cursor)
Modify
cursor
.next
temp
Modify
cursor
temp
Linked List – Delete (Cursor)
Find
before
such that
before
.next
= cursor
Modify
before
.next
cursor
.next
Doubly Linked List
Linked list where
Element has predecessor
successor
Issues
Easy to find preceding / succeeding elements Extra work to maintain links (for insert / delete) More storage per node
Doubly Linked List – Insertion
Example Must update references in
both
predecessor
and successor nodes
Restricted Abstractions
Restricting the operations an abstractionsupports can be a good thing
Efficiently supporting only a few operationsefficiently is easier If limited abstraction is sufficient, easier to reasonabout limited abstraction than a more general one
Restricted list abstractions
Stack (aka LIFO queue) Queue (aka FIFO queue) Dequeue (aka double ended queue)
Stack
Stack operations
Push = add element (to top) Pop = remove element (from top)