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CSC 301.01, Class 01: An introduction to the coure

Overview

  • Preliminaries
    • Notes and news
    • Upcoming work
    • Extra credit
    • Questions
  • Course goals
  • Course format
  • Approaching algorithms.
  • Problem: Getting from here to there
  • Problem: Optimal soldering plans
  • Problem: Scheduling overlapping tasks

News / Etc.

  • Welcome back! I look forward to having an excellent semester with you all.
  • I will take quick attendance.
  • I expect all of you to sign the department’s academic honesty policy. Please turn it in by Wednesday.
  • As is typical for the start of the semester, the course Web site is in rougher shape than I would like. Expect it to take form over the next few weeks.
  • I will be using the white board more than in other classes, particularly since I will be drawing data structures. Do you want to share daily note-taking responsibilities? We will revisit the question on Monday.
  • Friday PSA.

Upcoming Work

  • Read chapter 1 of Skiena by Monday.
  • Homework 1, due Wednesday

Extra Credit

Academic

  • CS Table, Tuesday, topic tbd.
  • CS Extras, Thursday, Contracts.

Peer

Good things to do

  • Ag days next Thursday.

Questions

How do we report on extra credits?
If you attend one, send me a short (one-to-two paragraph) email within two days of the event.
I prefer that you send me announcements in advance of class.

Course Goals

  • Think of it as “207, enhanced/extended/made more challenging”
  • Learn how to design and analyze algorithms and data structures.
    • Tools (methodologies for design, examples)
    • Verification techniques
    • Think about efficiency and how you analyze it carefully
  • More of the core literature
    • You already know trees, merge sort, Quicksort, binary search map/reduce, priority queues, priority queues implemented as heaps,

Detour priority queues

Idea: Implement priority queues as lists that are sorted from highest priority to lowest.

  • Add “Learn about heaps, priority 5”
  • List with (heaps/5) at the front.
  • Add “Study for the CSC 301 final, priority 1000”
  • List of the form [(heaps/5),(301final/1000)]
  • How much time does it take to put something in the right place in this list?
    • O(n^2)
    • O(nlogn)
    • O(n)
    • O(logn) (+1)
    • O(1)

Course Format

Often, Sam will pose problems and let you work on them and present them.

  • Incredibly supportive random calling on people
  • Small group work

Approaching Algorithms

You are now experienced computer science students. When some gives you a problem that admits an algorithmic solution, what do you do?

Think->Pair->Share

Approach one -> Getting from point A to point B

  • There are places along the way from point A to point B, think about the places along the way and how you get from point A to the next point to the next …
  • More generally, break the problem up into smaller problems.
  • Once you have a solution, go back and see if you can make it better.
  • Top-down decomposition

Approach two -> Just try something

  • Kind of like freewriting in English. Get something out there.

Approach three -> Use the literature

  • Identify similar problems that might give you insight on how to solve this problem.

Approach four -> Try examples

  • Solve some examples of the problem by hand to gain insight.

Approach five -> Use a standard algorithm design strategy

  • Divide and conquer
  • Greed
  • We wll learn others

Additional things to help any approach

  • Make sure that you understand the problem
    • Formal specs
    • Unit tests
    • Talking to people
  • Draw pictures
  • Make sure that it’s correct
  • Consider how efficient it is

Problem: Getting From Here to There

  • Let’s pretend that net neturality is eliminated.
  • We now have a problem: We need to get information from place to place, and we may want the least expensive path, or the quickest, or …

We start by modeling the the problem

  • How do you represent/think about the input?
  • This is probably a weighted graph problem.
  • A graph is a collection of points (“nodes”, “vertices”) that have connections between them (“edges”).
  • Weighted graphs include a value associated with each edge.
  • Problem: Find the path (sequence of edges) from A to B with the least total cost.

Problem: Optimal Soldering Plans

Skipped

Stolen/modified from Skienna

  • We have a bunch of points that we need to have a robot solder on a circuit board.
  • We want the least wear and tear on the robot.
  • How do we determine how to order the points?

Problem: Scheduling Overlapping Tasks

Skipped

Stolen/modified from Skienna

  • You have a bunch of tasks, each of which has a start time and a length.
  • You can only do one task at a time.
  • How do you maximize the number of tasks you complete?

Extension

  • What if each task also has a value? How do you maximize the value of the tasks you complete?