Class 01: An Introduction to Algorithms

Held: Thursday, 28 August 2003

We begin the class by considering the discipline of CS and by trying to formally give instructions for an everyday problem.

Overview:

• Introduction; What is CS?
• An algorithm for making sandwiches.
• The parts of an algorithm.

An Introductory Question

• Rather than telling you exactly what the class is about, I'm going to start the class with a question for you.
  • The question will help ground the class.
  • The question will begin to get you used to some aspects of my teaching style (particularly my reliance on recitation-style work).
  • The question will test your abilities as a liberal artist.
• What is Computer Science?
• I will give some of my own responses after I've heard some of yours.

What is CS?

• Computer scientists differ in how they define the discipline. However, most would aggree that

  Computer science is the study of algorithms and data structures.

• By algorithms, we mean sets of instructions that can be used to solve problems.
  • Some problems are mathematical. For example, you might write an algorithm to find the square root of a real number.
  • Other problems deal with textual information. For example, you might write an algorithm that tells how to find a name in the phone book.
  • You can write algorithms for a wide variety of problems.
• By data structures, we mean mechanisms for organizing information. For example, we organize some information in lists and other information in tables.
• By study, we mean specify, design, describe, evaluate mathematically, evaluate experimentally, implement in software, implement in hardware, prove properties, consider applications and implications, and much, much more.
• In our studies, we rely on the tools and techniques from a number of other disciplines.
  • From mathematics, we take proof techniques, formal language for describing problems and solutions, and even core ideas.
  • From science, we take experimental techniques.
  • From engineering, we take techniques for designing and constructing things.
  • From psychology and the social sciences, we take techniques for understanding the relationship of our work to human endeavors.
• These diverse perspectives and skill sets make CS interesting and challenging.

An Everyday Algorithm

• We'll explore the problems of writing clear instructions through a simple exercise.
• Challenge: Write a clear, unambiguous, and detailed set of instructions for making a peanut butter and jelly sandwich.
• Format: Work in groups of about four.
• Each group will write its solution on one of the four boards.
• SamR will play the role of the sentient, but malicious and clueless follower of instructions.