Advent of Code 2019 in Python / Jupyter Notebook

This year I'll be using Advent of Code to learn Python. As my goal is more Deep Learning, than Python programming itself, I'll be doing AoC in Jupyter Notebook.

Goals:

• Learn Python tricks.
• Learn Jupyter Notebook tricks.
• Make it look pretty on GitHub.

Quirks & tricks

While Python resembles CoffeeScript - my favorite language so far (well, vice versa in reality: CoffeeScript resembles Python), Python has many legacy design decisions you have to adapt to. To name a few:

• Order of blocks in short form of if:

  <code_true> if <condition> else <code_false>
  
  # it gets weird for nested conditionals
  <true_1> if <cond_1> else <false_1_true_2> if <cond_2> else <false_1_false_2>

  In CoffeeScript it's:

  <code_true> if <condition>
  # or
  if <condition> then <code_true> else <code_false>
  
  # and for nested
  if <cond_1> then <true_1> else if <cond_2> then <false_1_true_2> else <false_1_false_2>

  While I clearly see why Python does that, it takes time to adapt to.

• No switch statement. Alternative is wordy:

  if x == 0:
      <code_0>
  elif x == 1:
      <code_1>
  elif x == 2:
      <code_2>
  else:
      <code_else>

• You can write:

  <code> for x in <range> if <condition>

  but you can't write:

  for x in <range> if <condition>:
      <code>

• Breaking outer loop has strange syntax, but I kinda like it:

  for <outer_loop>:
      for <inner_loop>:
          if <condition>: break
      else:
          # inner loop completed without breaking
          <code>

• Numbers in Python are not just arbitrary precision floating point bignums, but complex numbers as well. I like how writing both parts is optional. Makes it easier to define directions in 2D:

  ds = [1, 1j, -1, -1j] # for Right, Up, Left, Down.

• Sets in Python are powerful.

  A = {1,2,3,4}
  B = {3,4,5}
  C = A - B # == {1,2}
  D = B - A # == {5}
  D = B | {1} # == {1,3,4,5}

• Python doesn't allow inline assignment operations. Following is not possible:

  for s in input.split('\n'):
      if (match = re.match(r'some number: (-?\d+)', s)) != None:
          # do something with match.group(1)
      elif (match = re.match(r'something else: (.+)', s)) != None:
          # do something with match.group(1)

  Instead you have to write something like:

  for s in input.split('\n'):
      match = re.match(r'some number: (-?\d+)', s)
      if match != None:
          # do something with match.group(1)
          continue
      match = re.match(r'something else: (.+)', s)
      if match != None:
          # do something with match.group(1)
          continue

  That's no longer true in Python 3.8, where you can use special "walrus operator" :=, introduced especially for inline assignments:

  for s in input.split('\n'):
      if (match := re.match(r'some number: (-?\d+)', s)) != None:
          # do something with match.group(1)
      elif (match := re.match(r'something else: (.+)', s)) != None:
          # do something with match.group(1)

All years AoC solutions

• 2022:
  • Go
• 2021:
  • Go
• 2020:
  • Läng & Python ✌😎
• 2019:
  • Python in Jupyter Notebook — love this one, as it shows pretty results on GitHub 👈 you are here
• 2018
  • Go
• 2017:
  • CoffeeScript 👈 first year I was doing AoC
  • Go — done in December 2018
• 2016:
  • CoffeeScript — done in December 2017
  • Go — done in January 2019, incomplete
• 2015:
  • CoffeeScript — done in December 2017

Useful links

• Advent of Code - obviously.

  • Scatterplot - timings of first 100 solvers for all AoC tasks.
  • Medals - top 3 positions for each task.
  • r/adventofcode - subreddit with solutions and discussions. Visualizations are nice.

• Other challenges/exercises:

  • Exercism - exercises in many language tracks. Submit code. Can see other solutions. Tasks are mostly trivial. Can request mentor to improve you coding style. I was very satisfied with Go mentor bitfield.
  • Codewars - programming tasks in many languages. Submit code. Can see other solutions. 1 kyu (hardest level) katas often question your understanding of language internals.
  • Project Euler - probably the oldest programming challenge resource. Heavily math-based. Submit answers.
  • CodinGame - programming tasks in many languages. Submit code and see resulting animation. Can see ofther solutions. Has bot battles, if you want competition.
  • CodeForces - coding contests several times a month. Similar to IT Olympics/Olympiads, but online. Can solve tasks in archive, if you don't want competition. Can participate in Virtual contests, if you want competition, but contest is over.
  • HackerRank - very wide range of challenges. Submit code. Many languages to choose from. Acceptance tests (and results of their execution) are hidden, which makes it more challenging. Practice, compete, prepare for coding interview, solve test tasks from employers. Competitions include long-running translation of challenges from Project Euler (currently first 245 tasks).
  • Will not include link to Topcoder, as their website now looks like marketing sh↓t. Never used, probably never will.