Introduction

This project contains solutions for Advent of Code.

The difficulty of these puzzles is usually less than competitive programming problems, i.e. CodeForces. Even you can calculate the answer by a pencil and paper. Test cases are very simple and examples include nearly everything that you need to care about. But some of them is hard.

And the author provides a very interesting website!

ps.

• Remember to call parseInt when parsing the input by regular expressions.
• Do not try to find answers by binary search. The server will reject your submission after you have failed too much times.
• Solve puzzles by brute force searching if it is hard to find reasonable algorithms. Go to Bogdanp/awesome-advent-of-code or visit reddit to get more hits.

How to run

By default, part is 1, and YEAR is the current year.

• [YEAR=2015] node index.js <day> [part] < input.txt
• [YEAR=2015] node index.js <day> [part] -f input.txt

Summary

For hardness: S(Simple), M(Middle), H(Hard).

2015 (Done!)

day	hardness	keywords
1	S/S	iteration
2	S/S	iteration
3	S/S	simulation
4	S/S	md5
5	S/S	filter strings
6	S/S	simulation
7	M/M	post-order tree traveling
8	S/S	string replacement
9	S/S	permutation
10	S/S	iteration
11	S/S	filter strings
12	S/S	recursion
13	S/S	permutation
14	S/S	simulation
15	S/S	permutation
16	S/S	filter
17	M/M	dynamic programming
18	S/S	simulation
19	S/H	iteration/special laws
20	M/M	find bound
21	M/M	permutation
22	H/H	dfs
23	S/S	cpu
24	M/M	dynamic programming
25	S/-	iteration

2016 (Done!)

day	hardness	keywords
1	S/S	simulation
2	S/S	simulation
3	S/S	filter
4	S/S	filter
5	S/S	md5
6	S/S	array operations
7	S/S	filter
8	S/S	simulation
9	S/S	string replacement/recursion
10	S/S	simulation
11	H/H	bfs, optimization
12	S/S	cpu
13	H/H	bfs
14	S/S	md5
15	S/S	iteration
16	S/S	iteration
17	M/M	md5, bfs
18	S/S	iteration
19	H/H	find laws/dynamic programming
20	M/M	merge intervals
21	S/S	simulation
22	S/H	filter/bfs with special laws
23	S/M	cpu/optimization
24	M/M	bfs, permutation
25	S/-	cpu, find first

2017 (Done!)

day	hardness	keywords
1	S/S	iteration
2	S/S	iteration
3	S/M	find laws/infinite grid
4	S/S	filter strings
5	S/S	iteration
6	S/S	simulation
7	S/S	tree simulation/recursion
8	S/S	simple cpu simulation
9	S/S	iteration
10	S/S	simulation
11	S/S	find laws/simulation
12	S/S	bfs
13	S/S	simulation/find first
14	S/M	iteration/bfs
15	S/S	iteration
16	S/M	simulation/find laws
17	S/S	iteration
18	S/M	cpu
19	S/S	simulation
20	S/M	find stable/filter collisions
21	M/M	iterate grid
22	S/S	infinite grid
23	S/H	cpu/assembly to filter primes
24	S/S	dfs
25	S/-	turing machine

2018 (Done!)

day	hardness	keywords
1	S/S	iteration
2	S/S	filter strings/sort then diff
3	S/S	rectangles overlap
4	M/M	simulation
5	S/S	merge with stack
6	M/S	simulation
7	S/M	typology sorting/simulation
8	S/S	string parsing/recursion
9	S/M	simulation
10	M/S	auto scale
11	S/M	find the max sum rectangle
12	S/S	simulation/find loop
13	S/S	simulation
14	S/S	iteration/string match
15	M/S	simulation/find bound
16	S/S	cpu
17	M/S	water simulation
18	S/S	simulation/find loop
19	S/S	cpu/find logic
20	S/S	parse regexp and bfs
21	S/S	cpu to find logic
22	S/M	dp/bfs
23	S/H	filter/max clique
24	S/S	simulation/find bound
25	S/-	bfs

2019 (Done!)

day	hardness	keywords
1	S/S	iteration
2	S/S	cpu
3	M/S	line cross
4	S/S	filter numbers
5	S/S	cpu
6	S/S	bfs/nearest common ancestor
7	S/M	cpu/generators
8	S/S	count numbers/print and see
9	M/S	big numbers cpu
10	M/M	check connectivity/sort by k
11	S/S	cpu count visited/print and see
12	S/M	n-object simulation/lcm
13	S/H	cpu output map/game simulation
14	S/S	typology sorting/binary search
15	S/S	bfs
16	S/M	fft simulation
17	S/M	find intersections/cut routes
18	M/H	shortest path
19	S/S	count/find
20	M/M	shortest path
21	M/H	boolean cpu programming
22	S/H	shuffle simulation/number theory
23	M/M	multiple cpus
24	S/S	life game simulation
25	M/-	cpu rpg

Different scripts for day 25,

• day25.js, normal program but has -i option to load commands
• day25-map.js, searching for all rooms
• day25-input.txt, according to the rooms map, collect items and go to the checkpoint room
• day25-drop.js, try each possible combinations of items to pass the weight check

2020 (Done!)

day	hardness	keywords
1	S/S	2 sum/3 sum
2	S/S	filter strings
3	S/S	count
4	S/S	filter strings
5	S/S	iteration/print and see
6	S/S	count
7	S/S	bfs
8	S/S	cpu
9	S/S	filter/two points
10	S/S	sort and count/dp
11	S/S	life games simulation
12	S/S	moving iteration
13	S/M	find min/number theory
14	S/S	bits iteration
15	S/S	iteration
16	S/S	filter/match
17	S/S	3d/4d life games simulation
18	S/S	arithmetic ast
19	S/M	regexp tree/special convertion
20	S/H	picture matching/pattern search
21	M/S	analyze insets
22	S/S	cards array iteration
23	S/S	array iteration
24	S/S	hex flip/life game simulation
25	S/-	number iteration

2021

2021

day	hardness	keywords
1	S/S	iteration
2	S/S	iteration
3	S/S	count and filter strings
4	S/S	simulate game
5	S/S	count grid points
6	S/M	simulate list/calculate
7	S/S	midpoint/find best position
8	S/M	filter length/analyse mapping
9	S/S	filter points/bfs
10	S/S	brackets matching
11	S/S	simulate grid
12	S/S	bfs to find ways
13	S/S	fold dots/print and see
14	S/M	iteration
15	S/S	shortest path
16	S/S	parse packages
17	S/S	simulate shoot
18	M/S	brackets iteration
19	M/S	coordinates match
20	S/S	iteration
21	S/S	simulate game
22	S/H	cube overlap/discretization
23	M/-	move boxes
24	H/S	cpu analyse
25	S/-	simulate

2022

day	hardness	keywords
1	S/S	find max
2	S/S	RSP game
3	S/S	find same character
4	S/S	segment overlap
5	S/S	stack simulation
6	S/S	scan string
7	S/S	file directory size, DFS
8	S/S	matrix scan
9	S/-	rope positions
10	S/S	simple cpu/draw letters
11	S/M	simulation/keep reminders
12	S/S	bfs
13	S/S	compare lists
14	M/M	sand simulation
15	S/M	count positions/merge segments
16	-/-	bfs
17	-/-	tetris
18	S/-	count cube surfaces
19	-/-	build robots
20	M/S	list iteration
21	S/M	dfs/binary search
22	S/-	simulate moving
23	S/S	grid iteration
24	-/-	bfs
25	S/-	base conversion

Bonus

Released at reddit. You can download input.txt directly from here.

• YEAR=2016 node index.js 26 < input.txt > bonus.out.1
• YEAR=2016 node index.js 8 2 < bonus.out.1

Thanks to

• petertseng, first met in reddit for 2016/day11, who also has full solutions in Ruby/Haskell/Rust/D.
• sguest, for solving 2018/day22, with JavaScript solutions of each year.
• albertobastos, for solving 2018/day15, with partial solutions of 2018 in JavaScript.
• kufii, provides a cool website to show 2019 JavaScript solutions.
• mcpower, also met in reddit for 2019/day22, and has solutions for 2016(partial)/17/18/19 in Python/Rust.
• romellem for solving 2021/day24, with most of years in JavaScript.