adventOfCode2023 🎄

You can find the puzzle inputs here: https://adventofcode.com/2023

Recap of my progress in Advent of Code so far:

• 2020: 10 days (19 ⭐)
• 2023: 22 days (36 ⭐)

What have I learned this year?

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I really liked summary thread on Reddit, particularly Leftfish's summary, and although mine won't be as detailed, I would still like to share a few words here.

Geometry Formulas:

• I found out about Shoelace and Pick's formula

• In the shoelace algorithm, we can use either just the polygon edges or all the points that define the shape.
• In the case of going clockwise the result will be negative.
• In Pick's formula the edges themselves are not enough - here the number of points inside the figure and on the edges is important.

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Data Structures & Algorithms:

• I became more familiar with deque (list-like container with fast appends and pops) which helps avoiding unnecessary recursion.
• I learned more about tracing the path in BFS and Dijkstra’s Algorithm.

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Python Insights:

• Simpler Debugging With F-Strings

I did not know that you can just add = to the end of an expression,and this will print both the expression and its value.

tmp = "Have a good day 😊!"

print(f"tmp = '{tmp}'")
print(f"{tmp = }")

Both prints will show the same output.

If interested, you can read more here → Python documentation and Post on Real Python.

• The in operator with a Pandas series will check the index.

In the task from day 11, when I wanted to filter a DataFrame using list comprehension, I encountered a problem. As it turned out: "#" not in data[:][col_ind] is not the same as: "#" not in list(data[:][col_ind])

The in operator on a pandas.Series checks whether something is in the index, just like it works with a dict. So, to get the behaviour I wanted, I had to convert pandas.Series to a list (as shown in the second example).

Below is a short example illustrating the diffrence.

import pandas as pd

data = pd.DataFrame({
    'A': [1, 2, 3],
    'B': [4, 5, 6],
    'C': [7, 8, 9]
})

filtred_columns_1 = [col for col in data.columns if 4 not in data[:][col]]
filtred_columns_2 = [col for col in data.columns if 4 not in list(data[:][col])]

print("Result (Expression 1):", filtred_columns_1)  # ['A', 'B', 'C']
print(4 in data[:]['B'])  # False

print("Result (Expression 2):", filtred_columns_2) # ['A', 'C']
print(4 in list(data[:]['B']))  # True

So our dataframe looks:

A	B	C
1	4	7
2	5	8
3	6	9

In first case, we received all columns, despite the fact that in second columns there is 4, because pandas.Series looks like this:

	B
0	4
1	5
2	6

Because there is no 4 in the indexes (0,1,2), the expression is evaluated to True.

Of coursem there are more Pandorable approaches, for example: data.columns[(data != 4).all()]

But the way this operated caught me off guard.

Here's a helpful StackOverflow question regarding this topic.

• I became more familiar with the Python's standard libraries: itertools and collections

I used namedtuples, deque, defaultdict, and Counter from collections, and combinations and pairwise from itertools.

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Version Control:

At some point, I realized that I had not taken into account the fact that if I named the folder Day_1, and when I create the Day_10 folder, the latter would be displayed above.

Because of this, I read more about git rebase and, as a result, renamed folders (Day_1 -> Day_01) without changing the dates in the commit.

• To do this, you cannot have any unsaved modification. You need to stash your changes or create a temporary commit: git commit -m "tmp"

• Then execute the command: git rebase --committer-date-is-author-date -i HEAD~1 Instead of using HEAD~2, you can use the notation HEAD^^. It is important to have in range the commit from which you want to start making changes. git rebase -i --root will start an interactive rebase of all commits from the beginning. To preserve the committer date you need to add the --committer-date-is-author-date flag. This flag does not preserve the committer date, but it makes the committer date equal to the author date (which is good enough for me).

• VIM will open. Press i to start insert mode. Put e before commit you want to make changes to and exit VIM (escape, then :wq).

• Make changes. If you want to remove file, use the following command: git rm --cached folder/file_name.txt

• When you finish, execute: git rebase --continue

• Then VIM will open, if you don't want to change the commit name, simply press escape, and then type :wq.

How to continue a Git rebase and skip editing the commit message? More here

Other

• I created Reddit acount.
• I learned how to create Sankey diagrams → https://sankeymatic.com/build/

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