Semester 2, Week 1

If you are coming to the NYC Harvard Hackathon tomorrow here are the details:

Date: Saturday, February 6
Time: 10am to 3pm
Location: Browning School, 52 East 62nd Street (between Park and Madison)

When you arrive please go into the building. I will be there early so I will see you inside. If you signed up with me, you are registered, so they will already be expecting you!

Bring a laptop if possible. But if you can’t no worries, there will be computers available there.


Welcome to the second semester of CS50! We are all moving on to Unit 3 and working on Problems 3-0: RNG, Problem 3-1: Fifteen(Part 1), Problem 3-2: Fifteen(Part 2) and Hacker Edition Problem 3-3: Fifteen(Part 3). Please note that in Unit 3, instead of google forms with aha moments, you will be submitting word or text documents with each program answer the questions in the program spec.

If you are starting on 3-0: RNG, be sure to watch the video on pipes first. Also please note that to “seed” the random number generator, you will do:


and that drand48 will return a float between 0 and 1.

float n = drand48();

If you are finished, or mostly finished with Fifteen before Saturday’s Hackathon, take a look at Problem 3-7: Scramble, so that you have a bit of familiarity with this problem in advance.