Implement 2024 day 21 part 2

Invent a unit test for it too, because why not, it's Christmas

2024/bonus/day25/main.tf

@@ -0,0 +1,23 @@
+variable "input" {
+  type = string
+}
+
+locals {
+  blocks = split("\n\n", chomp(var.input))
+  heights = [
+    for block in local.blocks : [
+      for i in range(5) : length([
+        for line in split("\n", block) : line if substr(line, i, 1) == "#"
+      ])
+    ]
+  ]
+
+  locks = [for i in range(length(local.blocks)) : local.heights[i] if startswith(local.blocks[i], "#####")]
+  keys  = [for i in range(length(local.blocks)) : local.heights[i] if !startswith(local.blocks[i], "#####")]
+
+  combined = concat([for lock in local.locks : [for key in local.keys : [for i in range(5) : lock[i] + key[i] <= 7]]]...)
+}
+
+output "part1" {
+  value = length([for combination in local.combined : combination if alltrue(combination)])
+}

2024/bonus/main.tf

@@ -87,3 +87,12 @@ module "day19" {
 output "day19_1" {
   value = module.day19.part1
 }
+
+module "day25" {
+  source = "./day25"
+  input  = file("../inputs/25.txt")
+}
+
+output "day25_1" {
+  value = module.day25.part1
+}

2024/bonus/tests.tftest.hcl

@@ -164,3 +164,20 @@ run "day19" {
     error_message = "Part1 output is wrong"
   }
 }
+
+run "day25" {
+  command = plan
+
+  module {
+    source = "./day25"
+  }
+
+  variables {
+    input = file("../tests/samples/25.txt")
+  }
+
+  assert {
+    condition     = output.part1 == 3
+    error_message = "Part1 output is wrong"
+  }
+}

2024/src/aoc/days/day21.py

@@ -0,0 +1,159 @@
+import functools
+from collections import Counter, defaultdict
+
+from . import SeparateRunner
+
+NUMPAD = {
+    "A": (3, 2),
+    "0": (3, 1),
+    "1": (2, 0),
+    "2": (2, 1),
+    "3": (2, 2),
+    "4": (1, 0),
+    "5": (1, 1),
+    "6": (1, 2),
+    "7": (0, 0),
+    "8": (0, 1),
+    "9": (0, 2),
+}
+
+DIRPAD = {
+    "A": (0, 2),
+    "^": (0, 1),
+    "<": (1, 0),
+    "v": (1, 1),
+    ">": (1, 2),
+}
+
+
+@functools.cache
+def shortest_numpad(from_: str, to: str) -> list[str]:
+    inverse = set(NUMPAD.values())
+    ay, ax = NUMPAD[from_]
+    by, bx = NUMPAD[to]
+
+    dx, dy = bx - ax, by - ay
+
+    sx = "<" if dx < 0 else ">"
+    sy = "^" if dy < 0 else "v"
+
+    if dx > 0 and (by, ax) in inverse or (ay, bx) not in inverse:
+        return abs(dy) * sy + abs(dx) * sx + "A"
+    else:
+        return abs(dx) * sx + abs(dy) * sy + "A"
+
+
+@functools.cache
+def shortest_dirpad(from_: str, to: str) -> str:
+    inverse = set(DIRPAD.values())
+    ay, ax = DIRPAD[from_]
+    by, bx = DIRPAD[to]
+
+    dx, dy = bx - ax, by - ay
+    sx = "<" if dx < 0 else ">"
+    sy = "^" if dy < 0 else "v"
+
+    if dx > 0 and (by, ax) in inverse or (ay, bx) not in inverse:
+        return abs(dy) * sy + abs(dx) * sx + "A"
+    else:
+        return abs(dx) * sx + abs(dy) * sy + "A"
+
+
+def encode_shortest_numpad(code: str) -> str:
+    pos = "A"
+
+    res = ""
+
+    for c in code:
+        res += shortest_numpad(pos, c)
+        # print(c, res)
+        pos = c
+
+    return res
+
+
+def encode_shortest_dirpad(code: str) -> str:
+    pos = "A"
+
+    res = ""
+
+    for c in code:
+        if pos != c:
+            res += shortest_dirpad(pos, c)
+        else:
+            res += "A"
+        pos = c
+
+    return res
+
+
+def decode(code: str, pad: dict[str, tuple[int, int]]) -> str:
+    result = ""
+    inverse = {v: k for k, v in pad.items()}
+
+    y, x = pad["A"]
+
+    for i, c in enumerate(code):
+        match c:
+            case "A":
+                result += inverse[y, x]
+            case "^":
+                y -= 1
+            case "v":
+                y += 1
+            case "<":
+                x -= 1
+            case ">":
+                x += 1
+
+        if (y, x) not in inverse:
+            raise ValueError(
+                f"""Moved off the board {x, y}, after processing {c}.
+                Path so far: {result} (from {code[:i]})"""
+            )
+
+    return result
+
+
+def count_steps(path: str, count: int) -> dict[str, int]:
+    cur = "A"
+    counts = defaultdict(int)
+
+    for c in path:
+        step = shortest_dirpad(cur, c)
+        cur = c
+        counts[step] += count
+
+    return counts
+
+
+class DayRunner(SeparateRunner):
+    @classmethod
+    def part1(cls, input: str) -> int:
+        result = 0
+        for code in input.strip().split("\n"):
+            numpad = encode_shortest_numpad(code)
+            robot1 = encode_shortest_dirpad(numpad)
+            robot2 = encode_shortest_dirpad(robot1)
+
+            result += int(code[:-1]) * len(robot2)
+
+        return result
+
+    @classmethod
+    def part2(cls, input: str, robots=25) -> int:
+        result = 0
+        for code in input.strip().split("\n"):
+            numpad = encode_shortest_numpad(code)
+            keypresses = Counter([numpad])
+
+            for _ in range(robots + 1):
+                new_presses = Counter()
+                for subroute, count in keypresses.items():
+                    new_presses.update(count_steps(subroute, count))
+
+                keypresses = new_presses
+
+            result += int(code[:-1]) * keypresses.total()
+
+        return result

2024/src/aoc/days/day25.py

@@ -0,0 +1,29 @@
+import numpy
+
+from . import CombinedRunner
+
+
+class DayRunner(CombinedRunner):
+    @classmethod
+    def run_both(cls, input: str) -> tuple[int, None]:
+        blocks = input.strip().split("\n\n")
+
+        keys = []
+        locks = []
+
+        for block in blocks:
+            grid = numpy.array(list(map(list, block.splitlines())))
+            heights = numpy.count_nonzero(grid == "#", axis=0)
+
+            if block.startswith("#####"):
+                locks.append(heights)
+            else:
+                keys.append(heights)
+
+        locks = numpy.stack(locks, axis=0)
+
+        fitting = sum(
+            numpy.count_nonzero(numpy.all((key + locks) <= 7, axis=1)) for key in keys
+        )
+
+        return fitting, None

2024/tests/samples/21.txt

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

2024/tests/samples/25.txt

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

2024/tests/test_day21.py

@@ -0,0 +1,55 @@
+import pytest
+
+from aoc.days.day21 import (
+    DayRunner,
+    encode_shortest_dirpad,
+    encode_shortest_numpad,
+)
+
+from . import get_data
+
+
+def test_encode_shortest_numpad() -> None:
+    assert encode_shortest_numpad("029A") in (
+        "<A^A>^^AvvvA",
+        "<A^A^>^AvvvA",
+        "<A^A^^>AvvvA",
+    )
+
+
+def test_encode_shortest_dirpad() -> None:
+    numpad_encoded = encode_shortest_numpad("029A")
+    assert len(encode_shortest_dirpad(numpad_encoded)) == len(
+        "v<<A>>^A<A>AvA<^AA>A<vAAA>^A"
+    )
+
+
+@pytest.mark.parametrize(
+    "code,answer",
+    [
+        (
+            "029A",
+            "<vA<AA>>^AvAA<^A>A<v<A>>^AvA^A<vA>^A<v<A>^A>AAvA^A<v<A>A>^AAAvA<^A>A",
+        ),
+        ("980A", "<v<A>>^AAAvA^A<vA<AA>>^AvAA<^A>A<v<A>A>^AAAvA<^A>A<vA>^A<A>A"),
+        (
+            "179A",
+            "<v<A>>^A<vA<A>>^AAvAA<^A>A<v<A>>^AAvA^A<vA>^AA<A>A<v<A>A>^AAAvA<^A>A",
+        ),
+        ("456A", "<v<A>>^AA<vA<A>>^AAvAA<^A>A<vA>^A<A>A<vA>^A<A>A<v<A>A>^AAvA<^A>A"),
+        ("379A", "<v<A>>^AvA^A<vA<AA>>^AAvA<^A>AAvA^A<vA>^AA<A>A<v<A>A>^AAAvA<^A>A"),
+    ],
+)
+def test_encode_shortest_dirpad_twice(code: str, answer: str) -> None:
+    numpad_encoded = encode_shortest_numpad(code)
+    robot1 = encode_shortest_dirpad(numpad_encoded)
+    robot2 = encode_shortest_dirpad(robot1)
+    assert len(robot2) == len(answer)
+
+
+def test_sample_part1() -> None:
+    assert DayRunner.part1(get_data(21)) == 126384
+
+
+def test_sample_part2() -> None:
+    assert DayRunner.part2(get_data(21), robots=2) == 126384

2024/tests/test_day25.py

@@ -0,0 +1,7 @@
+from aoc.days.day25 import DayRunner
+
+from . import get_data
+
+
+def test_sample_part1() -> None:
+    assert DayRunner.part1(get_data(25)) == 3