Hashcode 2020 solution (Qualification round)

Our solution for the 2020 Google Hashcode qualification round problem with libraries and books.

Results

File	Score
a_example (input | output)	21
b_read_on (input | output)	5,822,900
c_incunabula (input | output)	5,645,747
d_tough_choices (input | output)	4,812,730
e_so_many_books (input | output)	5,019,670
f_libraries_of_the_world (input | output)	5,240,161
Total	26,541,229

The problem

You can find the pdf with the problem here.

Our solution

The code for the solution is in main.py. Our approach was a greedy algorithm.

The solution follows these steps:

1. Read the input

2. Calculate a heuristic score for each library with this formula:

   

   where library_books_score is calculated like this:

   1. Calculate available days for this library:

   

   2. Count how many books can be scanned in these days:

   

   3. Get the top k books according to their score and sum their scores. This is the library_books_score.

3. Sort libraries according to their score

4. For every library in sorted order:

   1. Count how many books from this library (k) can be scanned, like in steps 2i and 2ii, but now take into account the number of # days from the previous libraries. So if the previous libraries have taken d total days for the #, then the formula from the step 2i becomes:

   

   2. From the books of this library, except the books that have already been scanned from the previous libraries, get the top k books according to their score and scan them.

5. Create the output

An improvement

You can find an improvement of this solution (total score: 26,922,702) in this repository:
https://github.com/tipavlos/Hashcode-2020-solution-Qualification-round

Our team

• Athanasios Bollas (Thanasis1101)
• Dimitrios Sviggas (lookatme3)
• Anastasios Temperekidis (Tasos Temp)
• Pavlos Tiritiris (tipavlos)