Nim

import ../aoc, strutils, sequtils, tables

type
  Rules = ref Table[int, seq[int]]

#check if an update sequence is valid
proc valid(update:seq[int], rules:Rules):bool =
  for pi, p in update:
    for r in rules.getOrDefault(p):
      let ri = update.find(r)
      if ri != -1 and ri < pi:
        return false
  return true

proc backtrack(p:int, index:int, update:seq[int], rules: Rules, sorted: var seq[int]):bool =
  if index == 0:
    sorted[index] = p
    return true
  
  for r in rules.getOrDefault(p):
    if r in update and r.backtrack(index-1, update, rules, sorted):
      sorted[index] = p
      return true
  
  return false

#fix an invalid sequence
proc fix(update:seq[int], rules: Rules):seq[int] =
  echo "fixing", update
  var sorted = newSeqWith(update.len, 0);
  for p in update:
    if p.backtrack(update.len-1, update, rules, sorted):
      return sorted
  return @[]

proc solve*(input:string): array[2,int] =
  let parts = input.split("\r\n\r\n");
  
  let rulePairs = parts[0].splitLines.mapIt(it.strip.split('|').map(parseInt))
  let updates = parts[1].splitLines.mapIt(it.split(',').map(parseInt))
  
  # fill rules table
  var rules = new Rules
  for rp in rulePairs:
    if rules.hasKey(rp[0]):
      rules[rp[0]].add rp[1];
    else:
      rules[rp[0]] = @[rp[1]]
      
  # fill reverse rules table
  var backRules = new Rules
  for rp in rulePairs:
    if backRules.hasKey(rp[1]):
      backRules[rp[1]].add rp[0];
    else:
      backRules[rp[1]] = @[rp[0]]
  
  for u in updates:
    if u.valid(rules):
      result[0] += u[u.len div 2]
    else:
      let uf = u.fix(backRules)
      result[1] += uf[uf.len div 2]

I thought of doing a sort at first, but dismissed it for some reason, so I came up with this slow and bulky recursive backtracking thing which traverses the rules as a graph until it reaches a depth equal to the given sequence. Not my finest work, but it does solve the puzzle :)

Nim

import ../aoc, strutils

type
  Cell* = tuple[x,y:int]

#the 8 grid direction
const directions : array[8, Cell] = [
  (1, 0), (-1, 0),
  (0, 1), ( 0,-1),
  (1, 1), (-1,-1),
  (1,-1), (-1, 1)
]

const xmas = "XMAS"

#part 1
proc searchXMAS*(grid:seq[string], x,y:int):int =
  #search in all 8 directions (provided we can find a full match in that direction)
  let w = grid[0].len
  let h = grid.len
  
  for dir in directions:
    # check if XMAS can even fit
    let xEnd = x + dir.x * 3
    let yEnd = y + dir.y * 3
    if xEnd < 0 or xEnd >= w or
       yEnd < 0 or yEnd >= h:
      continue;
    
    #step along direction
    var matches = 0
    for s in 0..3:
      if grid[y + dir.y * s][x + dir.x * s] == xmas[s]:
        inc matches
        
    if matches == xmas.len:
      inc result

#part 2
proc isMAS(grid:seq[string], c, o:Cell):bool=
  let ca : Cell = (c.x+o.x, c.y+o.y)
  let cb : Cell = (c.x-o.x, c.y-o.y)
  let a = grid[ca.y][ca.x]
  let b = grid[cb.y][cb.x]
  (a == 'M' and b == 'S') or (a == 'S' and b == 'M')

proc searchCrossMAS*(grid:seq[string], x,y:int):bool =
  grid[y][x] == 'A' and
  grid.isMAS((x,y), (1,1)) and
  grid.isMAS((x,y), (1,-1))

proc solve*(input:string): array[2,int] =
  let grid = input.splitLines
  let w = grid[0].len
  let h = grid.len
  
  #part 1
  for y in 0..<h:
    for x in 0..<w:
      result[0] += grid.searchXMAS(x, y)
  
  #part 2, skipping borders
  for y in 1..<h-1:
    for x in 1..<w-1:
      result[1] += (int)grid.searchCrossMAS(x, y)

Part 1 was done really quickly. Part 2 as well, but the result was not accepted…

Turns out +MAS isn’t actually a thing :P

Nim

import ../aoc, re, sequtils, strutils, math

proc mulsum*(line:string):int=
  let matches = line.findAll(re"mul\([0-9]{1,3},[0-9]{1,3}\)")
  let pairs = matches.mapIt(it[4..^2].split(',').map(parseInt))
  pairs.mapIt(it[0]*it[1]).sum

proc filter*(line:string):int=
  var state = true;
  var i=0
  while i < line.len:
    if state:
      let off = line.find("don't()", i)
      if off == -1:
        break
      result += line[i..<off].mulsum
      i = off+6
      state = false
    else:
      let on = line.find("do()", i)
      if on == -1:
        break
      i = on+4
      state = true
      
  if state:
    result += line[i..^1].mulsum

proc solve*(input:string): array[2,int] =
  #part 1&2
  result = [input.mulsum, input.filter]

I had a nicer solution in mind for part 2, but for some reason nre didn’t want to work for me, and re couldn’t give me the start/end or all results, so I ended up doing this skip/toggle approach.

Also initially I was doing it line by line out of habit from other puzzles, but then ofc the don't()s didn’t propagate to the next line.

Nim

import strutils, times, sequtils, sugar

# check if level transition in record is safe
proc isSafe*(sign:bool, d:int): bool =
  sign == (d>0) and d.abs in 1..3;

#check if record is valid
proc validate*(record:seq[int]): bool =
  let sign = record[0] > record[1];
  return (0..record.len-2).allIt(isSafe(sign, record[it] - record[it+1]))

# check if record is valid as-is
# or if removing any item makes the record valid
proc validate2*(record:seq[int]): bool =
  return record.validate or (0..<record.len).anyIt(record.dup(delete(it)).validate)

proc solve*(input:string): array[2,int] =
  let lines = input.readFile.strip.splitLines;
  let records = lines.mapIt(it.splitWhitespace.map(parseInt));
  result[0] = records.countIt(it.validate);
  result[1] = records.countIt(it.validate2);

I got stuck on part 2 trying to check everything inside a single loop, which kept getting more ugly. So then I switched to just deleting one item at a time and re-checking the record.

Reworked it after first finding the solution to compress the code a bit, though the range iterators don’t really help with readability.

I did learn about the sugar import, which I used to make the sequence duplication more compact: record.dup(delete(it).

The real issue is already going 3 months without source control.

https://wooting.io/

No macro keys on the left, but the whole keyboard can be macro-ed. Also the hall effect switches are just about indestructible.

Maybe mermaid fits your use case?

https://mermaid.js.org/

That’s called R&D, Research and Development. As long as you learn from a failure, it is progress towards success.

Reminds me of this gem: https://lizengland.com/blog/2014/04/the-door-problem/

Heavy stuff first, cold things together, fragile stuff last.

Fork is great!

winget install Mozilla.Firefox

No need to even open Edge or Chrome

This can actually be caused by using mixed line endings. Which is a whole new class of horrible.

I think you mean this one?

https://xkcd.com/927/