Advent of Code 2015 Main Page | Tests 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 🏆 48/50 Day Problem Page Status Difficulty Solution Page Test Page Tags 1 Not Quite Lisp 🥇 ❄️ day_01.ex day_01_test.exs sequence, rust 2 I Was Told There Would Be No Math 🥇 ❄️ day_02.ex day_02_test.exs geometry2d, rust 3 Perfectly Spherical Houses in a Vacuum 🥇 ❄️ day_03.ex day_03_test.exs grid, set, rust 4 The Ideal Stocking Stuffer 🥇 ❄️ ❄️ day_04.ex day_04_test.exs md5, annoying 5 Doesn't He Have Intern-Elves For This? 🥇 ❄️ day_05.ex day_05_test.exs string 6 Probably a Fire Hazard 🥇 ❄️ ❄️ ❄️ day_06.ex day_06_test.exs grid, vector, reduction, slow 7 Some Assembly Required 🥇 ❄️ ❄️ ❄️ day_07.ex day_07_test.exs genserver, data-modelling, op-code 8 Matchsticks 🥇 ❄️ ❄️ ❄️ day_08.ex day_08_test.exs string-encoding, annoying 9 All in a Single Night 🥇 ❄️ ❄️ day_09.ex day_09_test.exs graph, routing 10 Elves Look, Elves Say 🥇 ❄️ day_10.ex day_10_test.exs string-encoding, sequence, reduction 11 Corporate Policy 🥇 ❄️ day_11.ex day_11_test.exs sequence, char-sequence, validation 12 JSAbacusFramework.io 🥇 ❄️ day_12.ex day_12_test.exs json 13 Knights of the Dinner Table 🥇 ❄️ ❄️ day_13.ex day_13_test.exs brute-force, combinatorics, slow 14 Reindeer Olympics 🥇 ❄️ ❄️ day_14.ex day_14_test.exs measurement, recursion, sequence 15 Science for Hungry People 🥇 ❄️ ❄️ ❄️ day_15.ex day_15_test.exs quadratic-time, not-fast-enough, sequence, needs-improvement 16 Aunt Sue 🥇 ❄️ ❄️ ❄️ day_16.ex day_16_test.exs hard-description, count 17 No Such Thing as Too Much 🥇 ❄️ ❄️ day_17.ex day_17_test.exs not-fast-enough, combinatorics 18 Like a GIF For Your Yard 🥇 ❄️ ❄️ ❄️ day_18.ex day_18_test.exs grid, map, not-fast-enough 19 Medicine for Rudolph 🥇 ❄️ ❄️ ❄️ day_19.ex day_19_test.exs not-fast-enough, needs-improvement, vector, random-access 20 Infinite Elves and Infinite Houses 🥇 ❄️ ❄️ ❄️ ❄️ day_20.ex day_20_test.exs slow, infinite-sequence, sequence 21 RPG Simulator 20XX 🥇 ❄️ ❄️ ❄️ ❄️ day_21.ex day_21_test.exs double-parse, data-modelling, combinatorics, strategy 23 Opening the Turing Lock 🥇 ❄️ ❄️ ❄️ day_23.ex day_23_test.exs op-code, emulation 24 It Hangs in the Balance 🥇 ❄️ ❄️ ❄️ ❄️ ❄️ day_24.ex day_24_test.exs not-fast-enough, power-set, ambiguous-solution 25 Let It Snow 🥇 ❄️ ❄️ ❄️ day_25.ex day_25_test.exs table-lookup, modular-arithmetic