Basic concepts

Data Structures: A Pseudocode Approach with C, Second Edition1
Chapter 1Chapter 1
Objectives
• Use pseudocode in the development of algorithms
• Understand the need for Abstract Data Type (ADT)
• Understand the implementation of ADTs
• Use void pointers and pointer to functions
• Understand the role of Big-O notation
Basic ConceptsBasic Concepts

Pseudocode
Pseudocode is an English-like representation of the algorithm logic. ItPseudocode is an English-like representation of the algorithm logic. It
consists of an extended version of the basic algorithmic constructs:consists of an extended version of the basic algorithmic constructs:
sequence, selection, and iterationsequence, selection, and iteration..
•Algorithm Header
•Purpose, Condition, and Return
•Statement Numbers
•Variables
•Statment Constructs
•Algorithm Analysis

The Abstract Data Type
An ADT consists of a data declaration packagedAn ADT consists of a data declaration packaged
together with the operations that are meaningfultogether with the operations that are meaningful
on the data while embodying the structuredon the data while embodying the structured
principles of encapsulation and data hiding. In this sectionprinciples of encapsulation and data hiding. In this section
we define the basic parts of an ADT.we define the basic parts of an ADT.
•Atomic and Composite Data
•Data Type
•Data Structure
•Abstract Data Type

Data Structure
Aggregation of atomic and composite data into a set with defined
relationships. Structure refers to a set of rules that hold the data
together.
• A combination of elements in which each is either a data type or another
data structure.
• A set of associations of relationship involving combined elements.
Example:

Abstract Data Type
 ADT users are NOT concerned with how the task is done but rather what it
can do.
 An abstract data type is a data declaration packaged together with the
operations that are meaningful for the data type.
 We encapsulate the data and the operations on the data, and then hide
them from the user.
 All references to and manipulation of the data in a data structure are handled
through defined interfaces to the structure.

Model for an Abstract Data Type
In this section we provide a conceptual
model for an Abstract Data Type (ADT).
• ADT Operation – passage like
• ADT Data Structure – controlled
entirely

ADT Implementations
There are two basic structures we can use to
implement an ADT list: arrays and linked lists.
In this section we discuss the basic
linked-list implementation.
• Array Implementation
• Linked List Implemenation

Generic Code for ADT
In this section we discuss and provide examples
of two C tools that are required to implement
an ADT.
• Pointer to Void
• Pointer to Function

(Continued)

Algorithm Efficiency
To design and implement algorithms, programmersTo design and implement algorithms, programmers
must have a basic understanding of what constitutesmust have a basic understanding of what constitutes
good, efficient algorithms.good, efficient algorithms.
Linear Loops
-Efficiency is a function of the number of intstructions.
- Loop update either adds or subtracts.
• Logarithmic Loops
-The controlling variable is either multiplied or divided in each iteration.
- The number of iteration is a function of the multiplier or divisor.
• Nested Loops
- The number of iterations is the total number which is the product of the number of
iterations in the inner loop and number of iterations in the outer loop.
• Big-O Notation
-Not concerned with exact measurement of efficiency but with the magnitude.
- A dominant factor determines the magnitute.

Basic concepts

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