day 25 puzzle 1

day22.py

@@ -0,0 +1,26 @@
+with open("res/inputs/day22.txt", "r") as f:
+    values = list(map(int, f.read().split("\n")))
+
+calls = 0
+
+def step(a, shift):
+    global calls
+    calls += 1
+    s = (a >> -shift) if shift < 0 else (a << shift)
+    return (s ^ a) & 0xffffff
+
+def rand(value):
+    b = step(value, 6)
+    c = step(b, -5)
+    d = step(c, 11)
+    return d
+
+
+total = 0
+for v in values:
+    for _ in range(2000):
+        v = rand(v)
+    total += v
+
+print(total)
+print(calls)

progress.yaml

@@ -28,3 +28,23 @@
   stars: 2
 15:
   stars: 2
+16:
+  stars: 0
+17:
+  stars: 1
+18:
+  stars: 2
+19:
+  stars: 2
+20:
+  stars: 1
+21:
+  stars: 0
+22:
+  stars: 1
+23:
+  stars: 2
+24:
+  stars: 1
+25:
+  stars: 1

res/examples/day16_1.txt

@@ -0,0 +1,15 @@
+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############

res/examples/day16_2.txt

@@ -0,0 +1,17 @@
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################

res/examples/day17_1.txt

@@ -0,0 +1,5 @@
+Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0

res/examples/day17_2.txt

@@ -0,0 +1,5 @@
+Register A: 2024
+Register B: 0
+Register C: 0
+
+Program: 0,3,5,4,3,0

res/examples/day18.txt

@@ -0,0 +1,25 @@
+5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0

res/examples/day19.txt

@@ -0,0 +1,10 @@
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb

res/examples/day20.txt

@@ -0,0 +1,15 @@
+###############
+#...#...#.....#
+#.#.#.#.#.###.#
+#S#...#.#.#...#
+#######.#.#.###
+#######.#.#...#
+#######.#.###.#
+###..E#...#...#
+###.#######.###
+#...###...#...#
+#.#####.#.###.#
+#.#...#.#.#...#
+#.#.#.#.#.#.###
+#...#...#...###
+###############

res/examples/day21.txt

@@ -0,0 +1,5 @@
+029A
+980A
+179A
+456A
+379A

res/examples/day22.txt

@@ -0,0 +1 @@
+123

res/examples/day23.txt

@@ -0,0 +1,32 @@
+kh-tc
+qp-kh
+de-cg
+ka-co
+yn-aq
+qp-ub
+cg-tb
+vc-aq
+tb-ka
+wh-tc
+yn-cg
+kh-ub
+ta-co
+de-co
+tc-td
+tb-wq
+wh-td
+ta-ka
+td-qp
+aq-cg
+wq-ub
+ub-vc
+de-ta
+wq-aq
+wq-vc
+wh-yn
+ka-de
+kh-ta
+co-tc
+wh-qp
+tb-vc
+td-yn

res/examples/day24_1.txt

@@ -0,0 +1,10 @@
+x00: 1
+x01: 1
+x02: 1
+y00: 0
+y01: 1
+y02: 0
+
+x00 AND y00 -> z00
+x01 XOR y01 -> z01
+x02 OR y02 -> z02

res/examples/day24_2.txt

@@ -0,0 +1,47 @@
+x00: 1
+x01: 0
+x02: 1
+x03: 1
+x04: 0
+y00: 1
+y01: 1
+y02: 1
+y03: 1
+y04: 1
+
+ntg XOR fgs -> mjb
+y02 OR x01 -> tnw
+kwq OR kpj -> z05
+x00 OR x03 -> fst
+tgd XOR rvg -> z01
+vdt OR tnw -> bfw
+bfw AND frj -> z10
+ffh OR nrd -> bqk
+y00 AND y03 -> djm
+y03 OR y00 -> psh
+bqk OR frj -> z08
+tnw OR fst -> frj
+gnj AND tgd -> z11
+bfw XOR mjb -> z00
+x03 OR x00 -> vdt
+gnj AND wpb -> z02
+x04 AND y00 -> kjc
+djm OR pbm -> qhw
+nrd AND vdt -> hwm
+kjc AND fst -> rvg
+y04 OR y02 -> fgs
+y01 AND x02 -> pbm
+ntg OR kjc -> kwq
+psh XOR fgs -> tgd
+qhw XOR tgd -> z09
+pbm OR djm -> kpj
+x03 XOR y03 -> ffh
+x00 XOR y04 -> ntg
+bfw OR bqk -> z06
+nrd XOR fgs -> wpb
+frj XOR qhw -> z04
+bqk OR frj -> z07
+y03 OR x01 -> nrd
+hwm AND bqk -> z03
+tgd XOR rvg -> z12
+tnw OR pbm -> gnj

res/examples/day25.txt

@@ -0,0 +1,39 @@
+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####

src/day16/puzzle1.typ

@@ -0,0 +1,67 @@
+#import "/src/utils.typ": *
+
+#let START = "S"
+#let END = "E"
+#let WALL = "#"
+#let EMPTY = "."
+
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let solve(input) = {
+  let grid = input.split("\n").map(l => l.clusters())
+  let w = grid.first().len()
+  let h = grid.len()
+
+  let (sx, sy) = (0, 0)
+  let (ex, ey) = (0, 0)
+  for y in range(h) {
+    for x in range(w) {
+      let c = grid.at(y).at(x)
+      if c == START {
+        (sx, sy) = (x, y)
+      } else if c == END {
+        (ex, ey) = (x, y)
+      }
+    }
+  }
+
+  let choices = ((sx, sy, 0, 0),)
+  let (x, y, dir, score) = (0, 0, 0, 0)
+  while choices.len() != 0 {
+    let min-score = calc.min(..choices.map(c => c.last()))
+    let i = choices.position(c => c.last() == min-score)
+    (x, y, dir, score) = choices.remove(i)
+    for (d, (dx, dy)) in offsets.enumerate() {
+      // Ignore backflips
+      if calc.abs(d - dir) == 2 {
+        continue
+      }
+      let (x2, y2) = (x + dx, y + dy)
+      let c = grid.at(y2).at(x2)
+      if c == WALL {
+        continue
+      }
+      let score2 = score + 1 + if d != dir {1000} else {0}
+      if c == END {
+        return score2
+      }
+      choices.push((x2, y2, d, score2))
+    }
+    break
+  }
+  return 0
+}
+
+#show-puzzle(
+  16, 1,
+  solve,
+  example: (
+    "1": 7036,
+    "2": 11048
+  )
+)

src/day17/puzzle1.typ

@@ -0,0 +1,87 @@
+#import "/src/utils.typ": *
+
+#let ADV = 0
+#let BXL = 1
+#let BST = 2
+#let JNZ = 3
+#let BXC = 4
+#let OUT = 5
+#let BDV = 6
+#let CDV = 7
+
+#let get-combo(regs, value) = {
+  if value >= 7 {
+    panic()
+  }
+  if value <= 3 {
+    return value
+  }
+  return regs.at(value - 4)
+}
+
+#let solve(input) = {
+  let (registers, program) = input.split("\n\n")
+
+  let regs = ()
+  for line in registers.split("\n") {
+    regs.push(
+      int(
+        line.split(": ")
+            .last()
+      )
+    )
+  }
+  program = program.split(": ")
+                   .last()
+                   .split(",")
+                   .map(int)
+
+  let out = ()
+  let pc = 0
+  while pc < program.len() {
+    let op = program.at(pc)
+    let val = program.at(pc + 1)
+    if op == ADV {
+      let num = regs.at(0)
+      let den = get-combo(regs, val)
+      let res = num.bit-rshift(den)
+      regs.at(0) = res
+    } else if op == BXL {
+      regs.at(1) = regs.at(1).bit-xor(val)
+    } else if op == BST {
+      regs.at(1) = get-combo(regs, val).bit-and(0b111)
+    } else if op == JNZ {
+      if regs.at(0) != 0 {
+        pc = val
+        continue
+      }
+    } else if op == BXC {
+      regs.at(1) = regs.at(1).bit-xor(regs.at(2))
+    } else if op == OUT {
+      out.push(get-combo(regs, val).bit-and(0b111))
+    } else if op == BDV {
+      let num = regs.at(0)
+      let den = get-combo(regs, val)
+      let res = num.bit-rshift(den)
+      regs.at(1) = res
+    } else if op == CDV {
+      let num = regs.at(0)
+      let den = get-combo(regs, val)
+      let res = num.bit-rshift(den)
+      regs.at(2) = res
+    } else {
+      panic("Unknown instruction " + str(op))
+    }
+    pc += 2
+  }
+
+  return out.map(str).join(",")
+}
+
+#show-puzzle(
+  17, 1,
+  solve,
+  example: (
+    "1": "4,6,3,5,6,3,5,2,1,0"
+  )
+)

src/day17/puzzle2.typ

@@ -0,0 +1,108 @@
+#import "/src/utils.typ": *
+
+#let ADV = 0
+#let BXL = 1
+#let BST = 2
+#let JNZ = 3
+#let BXC = 4
+#let OUT = 5
+#let BDV = 6
+#let CDV = 7
+
+#let ops = ("ADV", "BXL", "BST", "JNZ", "BXC", "OUT", "BDV", "CDV")
+
+#let get-combo(regs, value) = {
+  if value >= 7 {
+    panic()
+  }
+  if value <= 3 {
+    return value
+  }
+  return regs.at(value - 4)
+}
+
+#let describe-combo(value) = {
+  if value == 7 {
+    return "<invalid>"
+  }
+  if value <= 3 {
+    return str(value)
+  }
+  return "ABC".at(value - 4)
+}
+
+#let describe(program) = {
+  let res = ""
+  res += program.map(str).join(",")
+
+  for i in range(0, program.len(), step: 2) {
+    res += "\n"
+    let op = program.at(i)
+    let val = program.at(i + 1)
+    let combo = describe-combo(val)
+
+    res += ops.at(op) + ": "
+    if op == ADV {
+      res += "A >>= " + combo
+    } else if op == BXL {
+      res += "B ^= " + str(val)
+    } else if op == BST {
+      res += "B = " + combo + " & 0b111"
+    } else if op == JNZ {
+      res += "IF A != 0 {PC = " + str(val) + "}"
+    } else if op == BXC {
+      res += "B ^= C"
+    } else if op == OUT {
+      res += "OUT(" + combo + " & 0b111)"
+    } else if op == BDV {
+      res += "B = A >> " + combo
+    } else if op == CDV {
+      res += "C = A >> " + combo
+    }
+  }
+  return res
+}
+
+#let solve(input) = {
+  let (registers, program) = input.split("\n\n")
+
+  let regs = ()
+  for line in registers.split("\n") {
+    regs.push(
+      int(
+        line.split(": ")
+            .last()
+      )
+    )
+  }
+  program = program.split(": ")
+                   .last()
+                   .split(",")
+                   .map(int)
+
+  let out = ()
+  let pc = 0
+
+  regs.first() = 0
+
+  for n in program {
+    let b = n
+  }
+  
+  return raw(block: true, describe(program))
+}
+
+Example:
+#solve(read(get-example-path(17, suffix: "2")))
+
+Input:
+#solve(get-input(17))
+
+/*
+#show-puzzle(
+  17, 2,
+  solve,
+  example: (
+    "2": 117440
+  )
+)*/

src/day18/puzzle1.typ

@@ -0,0 +1,143 @@
+#import "/src/utils.typ": *
+
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let get-lowest(nodes, scores) = {
+  let lowest-score = none
+  let lowest-i = none
+  for (i, (x, y)) in nodes.enumerate() {
+    let score = scores.at(y).at(x)
+
+    if lowest-i == none or score < lowest-score {
+      lowest-score = score
+      lowest-i = i
+    }
+  }
+
+  if lowest-i == none {
+    panic()
+  }
+  return lowest-i
+}
+
+#let make-path(parents, end) = {
+  let path = (end,)
+  let (x, y) = end
+  let pos = parents.at(y).at(x)
+  while pos != none {
+    (x, y) = pos
+    path.insert(0, pos)
+    pos = parents.at(y).at(x)
+  }
+  return path
+}
+
+#let find-path(w, h, grid) = {
+  let end = (w - 1, h - 1)
+  let (x, y) = (0, 0)
+  let open = ((x, y),)
+  let closed = ()
+  let g-scores = ((0,) * w,) * h
+  let f-scores = ((calc.inf,) * w,) * h
+  let parents = ((none,)*w,)*h
+  while open.len() != 0 {
+    let cur = open.remove(get-lowest(open, f-scores))
+    
+    if cur == end {
+      return make-path(parents, cur)
+    }
+
+    let g-score = g-scores.at(y).at(x)
+    let f-score = f-scores.at(y).at(x)
+    
+    let (x, y) = cur
+    for (dx, dy) in offsets {
+      let (x2, y2) = (x + dx, y + dy)
+      if x2 < 0 or x2 >= w or y2 < 0 or y2 >= h {
+        continue
+      }
+      if grid.at(y2).at(x2) {
+        continue
+      }
+      if (x2, y2) in closed {
+        continue
+      }
+      let g = x2 + y2
+      let h = calc.abs(end.first() - x2) + calc.abs(end.last() - y2)
+      let f = g + h
+
+      if f < f-scores.at(y2).at(x2) {
+        g-scores.at(y2).at(x2) = g
+        f-scores.at(y2).at(x2) = f
+        parents.at(y2).at(x2) = (x, y)
+        open.push((x2, y2))
+      }
+    }
+    closed.push(cur)
+  }
+  panic("No path was found")
+}
+
+#let solve(input, w: 0, h: 0, n-bytes: 0) = {
+  assert(w != 0, message: "Width cannot be 0")
+  assert(h != 0, message: "Height cannot be 0")
+  let grid = ((false,) * w,) * h
+
+  let obstacles = input.split("\n")
+  for obs in obstacles.slice(0, n-bytes) {
+    let (x, y) = obs.split(",").map(int)
+    grid.at(y).at(x) = true
+  }
+
+  let path = find-path(w, h, grid)
+  return path.len() - 1
+}
+
+#let visualize(input, w: 0, h: 0, n-bytes: 0, s: 2em) = {
+  let grid_ = ((false,) * w,) * h
+
+  let obstacles = input.split("\n")
+  for obs in obstacles.slice(0, n-bytes) {
+    let (x, y) = obs.split(",").map(int)
+    grid_.at(y).at(x) = true
+  }
+
+  let path = find-path(w, h, grid_)
+  for (x, y) in path {
+    grid_.at(y).at(x) = grid.cell(fill: green.lighten(60%))[O]
+  }
+  
+  let cells = grid_.flatten().map(c => {
+    if c == false []
+    else if c == true {grid.cell(fill: red.lighten(60%))[\#]}
+    else {c}
+  })
+  
+  grid(
+    columns: (s,) * w,
+    rows: (s,) * h,
+    align: center + horizon,
+    stroke: black,
+    ..cells
+  )
+}
+
+#show-puzzle(
+  18, 1,
+  solve.with(w: 71, h: 71, n-bytes: 1024),
+  example: (
+    (result: 22, args: (w: 7, h: 7, n-bytes: 12)),
+  ),
+  visualize: visualize.with(w: 7, h: 7, n-bytes: 12)
+)
+
+/*
+#pagebreak()
+#set page(width: auto, height: auto)
+#visualize(get-input(18), w: 71, h: 71, n-bytes: 1024, s: 1em)
+*/

src/day18/puzzle2.typ

@@ -0,0 +1,117 @@
+#import "/src/utils.typ": *
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let get-lowest(nodes, scores) = {
+  let lowest-score = none
+  let lowest-i = none
+  for (i, (x, y)) in nodes.enumerate() {
+    let score = scores.at(y).at(x)
+
+    if lowest-i == none or score < lowest-score {
+      lowest-score = score
+      lowest-i = i
+    }
+  }
+
+  if lowest-i == none {
+    panic()
+  }
+  return lowest-i
+}
+
+#let make-path(parents, end) = {
+  let path = (end,)
+  let (x, y) = end
+  let pos = parents.at(y).at(x)
+  while pos != none {
+    (x, y) = pos
+    path.insert(0, pos)
+    pos = parents.at(y).at(x)
+  }
+  return path
+}
+
+#let find-path(w, h, grid, start: (0, 0), end: auto) = {
+  let end = if end == auto {(w - 1, h - 1)} else {end}
+  let (x, y) = start
+  let open = ((x, y),)
+  let closed = ()
+  let g-scores = ((0,) * w,) * h
+  let f-scores = ((calc.inf,) * w,) * h
+  let parents = ((none,)*w,)*h
+  while open.len() != 0 {
+    let cur = open.remove(get-lowest(open, f-scores))
+    
+    if cur == end {
+      return true
+    }
+
+    let g-score = g-scores.at(y).at(x)
+    let f-score = f-scores.at(y).at(x)
+    
+    let (x, y) = cur
+    for (dx, dy) in offsets {
+      let (x2, y2) = (x + dx, y + dy)
+      if x2 < 0 or x2 >= w or y2 < 0 or y2 >= h {
+        continue
+      }
+      if grid.at(y2).at(x2) {
+        continue
+      }
+      if (x2, y2) in closed {
+        continue
+      }
+      let g = calc.abs(x2 - start.first()) + calc.abs(y2 - start.last())
+      let h = calc.abs(end.first() - x2) + calc.abs(end.last() - y2)
+      let f = g + h
+
+      if f < f-scores.at(y2).at(x2) {
+        g-scores.at(y2).at(x2) = g
+        f-scores.at(y2).at(x2) = f
+        parents.at(y2).at(x2) = (x, y)
+        open.push((x2, y2))
+      }
+    }
+    closed.push(cur)
+  }
+  return false
+}
+
+#let solve(input, w: 0, h: 0, n-bytes: 0) = {
+  assert(w != 0, message: "Width cannot be 0")
+  assert(h != 0, message: "Height cannot be 0")
+  let grid = ((false,) * w,) * h
+
+  let obstacles = input.split("\n")
+  let a = 0
+  let b = obstacles.len()
+
+  while b - a > 1 {
+    let m = calc.div-euclid(a + b, 2)
+    let grid2 = grid
+    for obs in obstacles.slice(0, m) {
+      let (x, y) = obs.split(",").map(int)
+      grid2.at(y).at(x) = true
+    }
+
+    if find-path(w, h, grid2) {
+      a = m
+    } else {
+      b = m
+    }
+  }
+  return obstacles.at(a)
+}
+
+#show-puzzle(
+  18, 2,
+  solve.with(w: 71, h: 71),
+  example: (
+    (result: "6,1", args: (w: 7, h: 7)),
+  )
+)

src/day19/puzzle1.typ

@@ -0,0 +1,41 @@
+#import "/src/utils.typ": *
+
+#let is-possible(target, towels: none) = {
+  if towels == none {
+    panic()
+  }
+
+  for towel in towels {
+    if towel == target {
+      return true
+    }
+    if target.starts-with(towel) {
+      if is-possible(target.slice(towel.len()), towels: towels) {
+        return true
+      }
+    }
+  }
+
+  return false
+}
+
+#let solve(input) = {
+  let (towels, targets) = input.split("\n\n")
+
+  towels = towels.split(", ")
+  let is-possible = is-possible.with(towels: towels)
+
+  let total = 0
+  for target in targets.split("\n") {
+    if is-possible(target) {
+      total += 1
+    }
+  }
+  return total
+}
+
+#show-puzzle(
+  19, 1,
+  solve,
+  example: 6
+)

src/day19/puzzle2.typ

@@ -0,0 +1,46 @@
+#import "/src/utils.typ": *
+
+#let solve(input) = {
+  let (towels, targets) = input.split("\n\n")
+
+  towels = towels.split(", ")
+  let by-initial = (:)
+  for towel in towels {
+    let initial = towel.first()
+    if initial not in by-initial {
+      by-initial.insert(initial, ())
+    }
+    by-initial.at(initial).push(towel)
+  }
+
+  let count(target) = {
+    let initial = target.first()
+    if initial not in by-initial {
+      return 0
+    }
+    let cnt = 0
+    for towel in by-initial.at(initial) {
+      if towel == target {
+        cnt += 1
+      } else if target.starts-with(towel) {
+        cnt += count(target.slice(towel.len()))
+      }
+    }
+
+    return cnt
+  }
+
+  let total = 0
+  for target in targets.split("\n") {
+    total += count(target)
+  }
+  return total
+}
+
+#show-puzzle(
+  19, 2,
+  solve,
+  example: 16,
+  only-example: true
+)
+#show-result(632423618484345)

src/day20/puzzle1.typ

@@ -0,0 +1,128 @@
+#import "/src/utils.typ": *
+
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let EMPTY = "."
+#let WALL = "#"
+#let START = "S"
+#let END = "E"
+
+#let in-grid(w, h, x, y) = {
+  return 0 <= x and x < w and 0 <= y and y < h
+}
+
+#let count-shortcuts(grid, w, h, save, path) = {
+  let in-grid = in-grid.with(w, h)
+  let total = 0
+  for (x1, y1) in path {
+    let v1 = grid.at(y1).at(x1)
+
+    for (dx1, dy1) in offsets {
+      let (x2, y2) = (x1 + dx1, y1 + dy1)
+      if not in-grid(x2, y2) {
+        continue
+      }
+      let v2 = grid.at(y2).at(x2)
+      if v2 < 0 {
+        for (dx2, dy2) in offsets {
+          let (x3, y3) = (x2 + dx2, y2 + dy2)
+          if not in-grid(x3, y3) {
+            continue
+          }
+          let v3 = grid.at(y3).at(x3)
+          if v3 > 0 {
+            if v3 - v1 >= save + 2 {
+              total += 1
+            }
+          }
+        }
+      }
+    }
+  }
+  return total
+}
+
+#let solve(input, save: 1) = {
+  let input-grid = input.split("\n").map(l => l.clusters())
+
+  let w = input-grid.first().len()
+  let h = input-grid.len()
+  let in-grid = in-grid.with(w, h)
+
+  let grid = ((-1,)*w,)*h
+  let start = none
+  let end = none
+  for y in range(h) {
+    for x in range(w) {
+      let c = input-grid.at(y).at(x)
+      if c == WALL {
+        continue
+      }
+      if c == START {
+        start = (x, y)
+      } else if c == END {
+        end = (x, y)
+      }
+      grid.at(y).at(x) = 0
+    }
+  }
+
+  let (x, y) = start
+  let (ex, ey) = end
+  let path = ()
+
+  while x != ex or y != ey {
+    path.push((x, y))
+    grid.at(y).at(x) = path.len()
+    for (dx, dy) in offsets {
+      let (x2, y2) = (x + dx, y + dy)
+      if not in-grid(x2, y2) {
+        continue
+      }
+      let v = grid.at(y2).at(x2)
+      if v == 0 {
+        (x, y) = (x2, y2)
+        break
+      }
+    }
+  }
+  path.push((x, y))
+  grid.at(y).at(x) = path.len()
+
+  return count-shortcuts(
+    grid, w, h,
+    save,
+    path
+  )
+}
+
+#let examples = (
+  (64, 1),
+  (40, 1),
+  (38, 1),
+  (36, 1),
+  (20, 1),
+  (12, 3),
+  (10, 2),
+  (8, 4),
+  (6, 2),
+  (4, 14),
+  (2, 14),
+)
+#let n-tot = 0
+#let examples2 = ()
+#for (save, cnt) in examples {
+  n-tot += cnt
+  examples2.push((result: n-tot, args: (save: save)))
+}
+
+#show-puzzle(
+  20, 1,
+  solve.with(save: 100),
+  example: examples2
+)

src/day21/puzzle1.typ

@@ -0,0 +1,100 @@
+#import "/src/utils.typ": *
+
+#let nums = (
+  "7": (0, 0),
+  "8": (1, 0),
+  "9": (2, 0),
+  "4": (0, 1),
+  "5": (1, 1),
+  "6": (2, 1),
+  "1": (0, 2),
+  "2": (1, 2),
+  "3": (2, 2),
+  "0": (1, 3),
+  "A": (2, 3),
+)
+
+#let arrows = (
+  "^": (1, 0),
+  "A": (2, 0),
+  "<": (0, 1),
+  "v": (1, 1),
+  ">": (2, 1),
+)
+
+#let get-num-path(code) = {
+  let path = ""
+  let (x, y) = nums.at("A")
+  for char in code {
+    let (x2, y2) = nums.at(char)
+    let dy = y2 - y
+    let dx = x2 - x
+    let ver = if dy == 0 {
+      ""
+    } else {
+      (if dy < 0 {"^"} else {"v"}) * calc.abs(dy)
+    }
+    let hor = if dx == 0 {
+      ""
+    } else {
+      (if dx < 0 {"<"} else {">"}) * calc.abs(dx)
+    }
+    path += if y == 3 and x2 == 0 {
+      ver + hor
+    } else {
+      hor + ver
+    } + "A"
+    (x, y) = (x2, y2)
+  }
+  return path
+}
+
+#let get-dir-path(code) = {
+  let path = ""
+  let (x, y) = arrows.at("A")
+  for char in code {
+    let (x2, y2) = arrows.at(char)
+    let dy = y2 - y
+    let dx = x2 - x
+    let ver = if dy == 0 {
+      ""
+    } else {
+      (if dy < 0 {"^"} else {"v"}) * calc.abs(dy)
+    }
+    let hor = if dx == 0 {
+      ""
+    } else {
+      (if dx < 0 {"<"} else {">"}) * calc.abs(dx)
+    }
+    path += if x == 0 and dy < 0 {
+      hor + ver
+    } else {
+      ver + hor
+    } + "A"
+    (x, y) = (x2, y2)
+  }
+  return path
+}
+
+#let get-path(code) = {
+  let num-path = get-num-path(code)
+  let dir-path-1 = get-dir-path(num-path)
+  let dir-path-2 = get-dir-path(dir-path-1)
+  return dir-path-2
+}
+
+#let solve(input) = {
+  let codes = input.split("\n")
+  let total = 0
+  for code in codes {
+    let len = get-path(code).len()
+    let num = int(code.slice(0, code.len() - 1))
+    total += len * num
+  }
+  return total
+}
+#show-puzzle(
+  21, 1,
+  solve,
+  example: 126384
+)

src/day22/puzzle1.typ

@@ -0,0 +1,61 @@
+#import "/src/utils.typ": *
+
+#let random(prev) = {
+  let step(a, shift) = {
+    let s = if shift < 0 {
+      a.bit-rshift(-shift)
+    } else {
+      a.bit-lshift(shift)
+    }
+    return s.bit-xor(a).bit-and(0xffffff)
+  }
+  let b = step(prev, 6)
+  let c = step(b, -5)
+  let d = step(c, 11)
+  return d
+}
+
+#let solve(input, steps: 1) = {
+  let values = input.split("\n").map(int)
+  let total = 0
+  for value in values {
+    for _ in range(steps) {
+      value = random(value)
+    }
+    total += value
+  }
+  return total
+}
+
+#let examples = ()
+#let results = (
+  15887950,
+  16495136,
+  527345,
+  704524,
+  1553684,
+  12683156,
+  11100544,
+  12249484,
+  7753432,
+  5908254
+)
+#for (i, res) in results.enumerate() {
+  examples.push((
+    result: res,
+    args: (steps: i + 1)
+  ))
+}
+
+#show-puzzle(
+  22, 1,
+  solve.with(steps: 2000),
+  example: examples,
+  only-example: true
+)
+
+#show-result(18261820068)
+
+//B = ((A << 6) ^ A) & 0xffffff\
+//C = ((B >> 5) ^ B) & 0xffffff\
+//D = ((C << 11) ^ C) & 0xffffff

src/day23/puzzle1.typ

@@ -0,0 +1,50 @@
+#import "/src/utils.typ": *
+
+#let solve(input) = {
+  let links = input.split("\n")
+
+  let links-dict = (:)
+
+  let to-test = ()
+  for link in links {
+    let (a, b) = link.split("-")
+    if a not in links-dict {
+      links-dict.insert(a, ())
+    }
+    if b not in links-dict {
+      links-dict.insert(b, ())
+    }
+    links-dict.at(a).push(b)
+    links-dict.at(b).push(a)
+    if a.starts-with("t") {
+      to-test.push(a)
+    }
+    if b.starts-with("t") {
+      to-test.push(b)
+    }
+  }
+
+  let total = 0
+  let groups = ()
+  for comp1 in to-test.dedup() {
+    for comp2 in links-dict.at(comp1) {
+      for comp3 in links-dict.at(comp2) {
+        if comp1 in links-dict.at(comp3) {
+          let group = (comp1, comp2, comp3).sorted()
+          if group not in groups {
+            total += 1
+            groups.push(group)
+          }
+        }
+      }
+    }
+  }
+
+  return total
+}
+
+#show-puzzle(
+  23, 1,
+  solve,
+  example: 7
+)

src/day23/puzzle2.typ

@@ -0,0 +1,104 @@
+#import "/src/utils.typ": *
+
+#let bron-kerbosch(links, R, P, X) = {
+  if P.len() == 0 and X.len() == 0 {
+    return if R.len() > 2 {
+      R.sorted()
+    } else {
+      none
+    }
+  }
+
+  let longest-len = 0
+  let longest = none
+  let to-visit = P
+  for v in to-visit {
+    let neighbors = links.at(v)
+    let clique = bron-kerbosch(
+      links,
+      R + (v,),
+      P.filter(n => n in neighbors),
+      X.filter(n => n in neighbors)
+    )
+    if clique != none {
+      let l = clique.len()
+      if longest == none or l > longest-len {
+        longest = clique
+        longest-len = l
+      }
+    }
+    let _ = P.remove(0)
+    X.push(v)
+  }
+  return longest
+}
+
+#let bron-kerbosch2(links, R, P, X) = {
+  if P.len() == 0 and X.len() == 0 {
+    return if R.len() > 2 {
+      R.sorted()
+    } else {
+      none
+    }
+  }
+
+  let pivot = if P.len() != 0 {
+    P.first()
+  } else {
+    X.first()
+  }
+  let pivot-neighbors = links.at(pivot)
+  let longest-len = 0
+  let longest = none
+  let to-visit = P.filter(n => n not in pivot-neighbors)
+  for v in to-visit {
+    let neighbors = links.at(v)
+    let clique = bron-kerbosch2(
+      links,
+      R + (v,),
+      P.filter(n => n in neighbors),
+      X.filter(n => n in neighbors)
+    )
+    if clique != none {
+      let l = clique.len()
+      if longest == none or l > longest-len {
+        longest = clique
+        longest-len = l
+      }
+    }
+    let _ = P.remove(P.position(n => n == v))
+    X.push(v)
+  }
+  return longest
+}
+
+#let solve(input) = {
+  let links = input.split("\n")
+
+  let links-dict = (:)
+
+  let to-test = ()
+  for link in links {
+    let (a, b) = link.split("-")
+    if a not in links-dict {
+      links-dict.insert(a, ())
+    }
+    if b not in links-dict {
+      links-dict.insert(b, ())
+    }
+    links-dict.at(a).push(b)
+    links-dict.at(b).push(a)
+  }
+
+  let clique = bron-kerbosch2(links-dict, (), links-dict.keys(), ())
+
+  return clique.join(",")
+}
+
+#show-puzzle(
+  23, 2,
+  solve,
+  example: "co,de,ka,ta",
+  only-example: true
+)
+#show-result("ab,al,cq,cr,da,db,dr,fw,ly,mn,od,py,uh")

src/day24/puzzle1.typ

@@ -0,0 +1,78 @@
+#import "/src/utils.typ": *
+
+#let solve(input) = {
+  let (inputs, gates) = input.split("\n\n")
+  let ids = ()
+  inputs = inputs.split("\n").map(i => {
+    let (id, value) = i.split(": ")
+    return (id: id, value: value == "1")
+  })
+  ids += inputs.map(i => i.id)
+  gates = gates.split("\n").map(g => {
+    let (gate, output) = g.split(" -> ")
+    let (i1, op, i2) = gate.split(" ")
+    return (
+      in1: i1,
+      in2: i2,
+      op: op,
+      out: output
+    )
+  })
+  let gates-by-id = (:)
+  for gate in gates {
+    gates-by-id.insert(gate.out, gate)
+  }
+
+  ids += gates.map(g => g.out)
+  ids = ids.dedup()
+  let dbg = (inputs, gates)
+
+  let values = (:)
+  for input in inputs {
+    values.insert(input.id, input.value)
+  }
+
+  let stack = ids.filter(id => id.starts-with("z"))
+  let output = (0,) * stack.len()
+  while stack.len() != 0 {
+    let v = stack.pop()
+    if v in values {
+      if v.starts-with("z") {
+        let i = int(v.slice(1))
+        output.at(i) = int(values.at(v))
+      }
+    } else {
+      stack.push(v)
+      let gate = gates-by-id.at(v)
+      if gate.in1 in values and gate.in2 in values {
+        let v1 = values.at(gate.in1)
+        let v2 = values.at(gate.in2)
+        let value = if gate.op == "AND" {
+          v1 and v2
+        } else if gate.op == "OR" {
+          v1 or v2
+        } else if gate.op == "XOR" {
+          (v1 or v2) and not (v1 and v2)
+        }
+        values.insert(v, value)
+      } else {
+        stack.push(gate.in1)
+        stack.push(gate.in2)
+      }
+    }
+  }
+
+  let result = output.rev()
+                     .fold(0, (a, b) => a.bit-lshift(1).bit-or(b))
+
+  return result
+}
+
+#show-puzzle(
+  24, 1,
+  solve,
+  example: (
+    "1": 4,
+    "2": 2024
+  )
+)

src/day25/puzzle1.typ

@@ -0,0 +1,61 @@
+#import "/src/utils.typ": *
+
+#let parse-schematic(schematic) = {
+  let lines = schematic.split("\n")
+  let is-key = "." in schematic.first()
+
+  let n-cols = lines.first().len()
+  let n-rows = lines.len()
+  let heights = ()
+
+  for x in range(n-cols) {
+    let y = if is-key {n-rows - 2} else {1}
+    let h = 0
+    for i in range(n-rows) {
+      if lines.at(y).at(x) == "." {
+        break
+      }
+      h += 1
+      y += if is-key {-1} else {1}
+    }
+    heights.push(h)
+  }
+
+  return (if is-key {"key"} else {"lock"}, heights)
+}
+
+#let fits(lock, key) = {
+  let tmp = lock.zip(key).map(p => p.sum())
+  return calc.max(..tmp) <= 5
+}
+
+#let solve(input) = {
+  let schematics = input.split("\n\n")
+
+  let locks = ()
+  let keys = ()
+  for schematic in schematics {
+    let (type, heights) = parse-schematic(schematic)
+    if type == "key" {
+      keys.push(heights)
+    } else {
+      locks.push(heights)
+    }
+  }
+  let total = 0
+  for key in keys {
+    for lock in locks {
+      if fits(lock, key) {
+        total += 1
+      }
+    }
+  }
+
+  return total
+}
+
+#show-puzzle(
+  25, 1,
+  solve,
+  example: 3
+)

src/utils.typ

@@ -197,8 +197,10 @@
   set text(font: "Source Sans 3")
   set page(
     footer: context {
+      if counter(page).get().first() != 1 {
         align(center, counter(page).display("1 / 1", both: true))
       }
+    }
   )
   body
 }