1. Coursenotes CS3114: Data Structures and Algorithms Clifford A. Shaffer Department of Computer Science Virginia Tech Copyright © 2008-2013

2. How to Survive Keys to success:  Keeping Track of all the details  You can’t remember it all  Rational Planning (and keeping to the plan)  Spread the work over time  Incremental Development  Interleave writing and debugging 2

3. Being Organized 1 Software development has so many details –Spec requirements –Program interactions So does Life –Assignments and other things to do 3

4. Being Organized 2 You can’t turn this on/off –Either you live an organized life, or you can’t succeed as a software developer –Part of it is developing the attitude of “sweating the details” –Part of it is having the coping mechanisms to handle the details 4

5. Memory Can’t Handle It Externalize –TODO lists (What) –Scheduling (The Plan for How) –Issue trackers –Documenting/Commenting –Be able to update lists at any time, Repository: GitHub 5

6. Spread Work Over Time For anything beyond a small software project, you must have a plan/schedule Explicitly develop a schedule: –Break into pieces: List of subtasks –Deadlines for subtasks –Realistic, enough flexibility built in –Continuously modify and refine the plan 6

7. Incremental Development 1 How to fail at implementing your project: 1.Write the project 2.Debug the project 7

8. Incremental Development 2 How to succeed: 1.Write the smallest possible kernel 2.Debug the kernel thoroughly 3.Repeat until completion: i.Add a functional unit ii.Debug the resulting program 4.Have a way to track details 8

9. Incremental Development 3 On any given day, write only as much code as you have time to debug THAT DAY This works well with Scheduling and Organizing 9

10. Recursion An algorithm is recursive if it calls itself to do part of its work. The key to success in recursion –Don’t think about the process –The recursive call is just another function call to do something

11. Induction Just like recursion –Base cases –Induction hypothesis is the recursive call (on a smaller version of the theorem) –Induction works because you get to “use” the induction hypothesis to do something.

12. 12 Estimation Techniques Known as “back of the envelope” or “back of the napkin” calculation 1.Determine the major parameters that effect the problem. 2.Derive an equation that relates the parameters to the problem. 3.Select values for the parameters, and apply the equation to yield and estimated solution.

13. 13 Estimation Example How many library bookcases does it take to store books totaling one million pages? Estimate: –Pages/inch –Feet/shelf –Shelves/bookcase