Data Structures Introduction

What is data? (Latin) Plural of datum = something given.

Data and Operations "Data" and "Operations" are to Computer Science as "Point" and "Line" are to Geometry. Undefined terms, the starting point.

Computers, Algorithms, Programs Computers are machines that perform operations on data Algorithms are sequences of operations to be performed on particular types of data in order to achieve a meaningful outcome. Programs are algorithms that are coded in a particular syntax or language such as Assembly, C++, Java, or Python

Data vs. information Data becomes information when it is structured in some way that has meaning.

Ways of structuring data Bit strings (0's and 1's) Integers Floating point numbers Logical values (True, False) Characters Strings Lists, Queues, Dequeus, Trees Files, pictures …

Operations Each data structure has its own set of operations. Integers: Add, multiply, divide, compare… Strings of characters Concatenate, print, compare, substrings…

In Data Structures, we study Ways of structuring data Abstract Data Types (ADT's) e.g. Lists, Stacks, Queues, Trees, Graphs Operations on those data types Algorithms to manipulate ADT's e.g. Searching, Sorting, Recursion

ADT's encapsulate. Implementation Interface User Operations Data & Algorithms.

List 10 random 2-digit integers >>>from random import randint >>>[randint(10,100) for i in range(10)] [87, 35, 52, 88, 87, 60, 19, 19, 26, 72] Examples of encapsulation: randint(a,b): An algorithm not in Python range(n): Implemention is built in to Python List: An abstract data type

Use of Abstract Data Types Separates the problem of implementation from that of manipulation Allows the programmer to solve problems without regard to implementation. Allows the programmer to alter the implementation without affecting problems already solved.

Understanding Data Structures Helps you write better programs Makes you a better problem solver Helps you use computers more efficiently Helps you maintain programs more effectively

Why Python? Fact: (Alan Turing) Any computer (with a minimal set of operations) can, with enough time and memory, perform any task any other computer can do. Any programming language (with a minimal set of operations) can implement any algorithm that any other programming language can implement.

Python Has an impressive set of built-in data structures. New data structures can be implemented relatively easily. Interpreted language. You can try anything before compiling.