Tuesday April 18th
4/18/17 - A Bit of Rest
Today I learned
- In C++, you can exit a programme gracefully by typing “return(0)”. Since you have int main() and it’s looking for a return int, you can insert it anywhere to exit. Sort of like system.exit or whatever in other programmes.
C++ homework done.
A few snippets of code. I didn’t include another three linked .h files here. Don’t want people to copy, etc.
Also, what my debugger looks like when the programme is run.
Things to get done
Look over some code for C++ and submit (hopefully) to my Lab —> done
Do some more work on my Programming for Correctness work. I’m currently on Split ranges
Get some rest tonight, and be fresh to work on Homework 6 (due 4/23)
A Kata Solved (note: this is in Python) :)
# In this Kata, you have to find the factors of integer # down to the limit including the limiting number. # If the limit is more than the integer, return an empty list def factors(integer, limit): # make an empty list arr =  # if limit exceeds integer, return an empty array if limit > integer: return  # else, find all the factors of the integer # between the limit and the integer # push those factors to the empty array else: for i in range(limit, integer+1): if integer % i == 0: arr.append(i) return arr
And now, another puzzle
How many balls would you need to assemble a regular tetrahedron, if the edge of the tetrahedron consists of x balls?
Write a function that takes the value and returns the count of balls needed.
The solution is an interesting one, based on a formula called “The Tetrahedral number”
Here is a visualization of the problem
Side top view packed balls
Bottom view of tetrahedron packed The last row is 4 balls long. Total is 20 for all balls counted
Btw I did these models in a 3D product/ architectural modelling programme I learned years ago called Rhino. This software is also used by car designers and people in the movie industry. I learned it from two persons; one of whom was an Art Director (who worked on Avatar and Star Trek) , and the other, who was a car designer (he designed grills for cars) for Honda.
also, check out another favourite site of mine, Math Stack Exchange:
Math Stack Exchange Tetrahedral number
As for the solution, this is in Python, too (sorry) :)
def count_balls(x): // the formula is : return x * ((x + 1) * (x + 2)) / 6
I figured out how to re-write fractions and limits in LaTeX. Here is my code for generating the Tetrahedral formula