Data Structures

Basic Terminologies

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Data Structures

“Clever” ways to organize information in order to enable efficient computation

– What do we mean by clever?– What do we mean by efficient?

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Definition

• Data Structure is a way of collecting and organizing data in such a way that we can perform operations on these data in an effective way. Data Structures is about rendering data elements in terms of some relationship, for better organization and storage.

• Data structures can implement one or more particular abstract data types (ADT), which are the means of specifying the contract of operations and their complexity.

Data Structures - Introduction 3

Picking the best Data Structure for the job

• The data structure you pick needs to support the operations you need

• Ideally it supports the operations you will use most often in an efficient manner

• Examples of operations:– A List with operations insert and delete– A Stack with operations push and pop

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Terminology• Abstract Data Type (ADT)– Mathematical description of an object with

set of operations on the object. Useful building block.

• Algorithm– A high level, language independent,

description of a step-by-step process• Data structure– A specific family of algorithms for

implementing an abstract data type.• Implementation of data structure– A specific implementation in a specific

language

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Terminology

• DataData refers to value or set of values.

e.g.Marks obtained by the students.

• Data typedata type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the

operations that can be done on values of that type; and the way

values of that type can be stored

Data Structures - Introduction 6

Terminology• Primitive data type:These are basic data types that are provided by theprogramming language with built-in support. These datatypes are native to the language. This data type issupported by machine directly

• VariableVariable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents.

Data Structures - Introduction 7

Terminology

• RecordCollection of related data items is known as record. The elements of records are usually Called fields or members .Records are distinguished from arrays by the fact that their number of fields is typically fixed, each field has a name, and that each field may have a different type.

• ProgramA sequence of instructions that a computer can interpret and execute.

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Terminology examples

• A stack is an abstract data type supporting push, pop and isEmpty operations

• A stack data structure could use an array, a linked list, or anything that can hold data

• One stack implementation is java.util.Stack; another is java.util.LinkedList

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Concepts vs. Mechanisms

• Abstract• Pseudocode• Algorithm– A sequence of high-

level, language independent operations, which may act upon an abstracted view of data.

• Abstract Data Type (ADT)– A mathematical

description of an object and the set of operations on the object.

• Concrete• Specific programming language• Program

– A sequence of operations in a specific programming language, which may act upon real data in the form of numbers, images, sound, etc.

• Data structure– A specific way in which a

program’s data is represented, which reflects the programmer’s design choices/goals. 10

Why So Many Data Structures?

Ideal data structure:“fast”, “elegant”, memory efficient

Generates tensions:– time vs. space– performance vs. elegance– generality vs. simplicity– one operation’s performance vs.

another’s The study of data structures is the study of tradeoffs. That’s why we have so many of them!

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