Day 15 (#24)

* Boilerplate

* Solve 15.a

* Solve 15.b

* Factor out code and fix a testing woopsie

aoc_2023/day_15/a.py

@@ -0,0 +1,29 @@
+from dataclasses import dataclass
+from aoc_2023.day_15.common import hash_it
+from aoc_2023.day_15.parser import Parser
+
+
+@dataclass
+class Day15PartASolver:
+    lines: list[str]
+
+    @property
+    def solution(self) -> int:
+        return sum(hash_it(line) for line in self.lines)
+
+
+def solve(input: str) -> int:
+    data = Parser.parse(input)
+    solver = Day15PartASolver(data)
+
+    return solver.solution
+
+
+def get_solution() -> int:
+    with open("aoc_2023/day_15/input.txt", "r") as f:
+        input = f.read()
+    return solve(input)
+
+
+if __name__ == "__main__":
+    print(get_solution())

aoc_2023/day_15/b.py

@@ -0,0 +1,108 @@
+from dataclasses import dataclass, field
+from functools import cached_property
+from typing import Optional
+from aoc_2023.day_15.common import hash_it
+from aoc_2023.day_15.parser import Parser
+
+
+@dataclass
+class Minus:
+    label: str
+
+
+@dataclass
+class Equal:
+    label: str
+    val: int
+
+
+@dataclass
+class Lens:
+    label: str
+    focus_length: int
+    deleted: bool = False
+
+
+@dataclass(frozen=True)
+class Box:
+    id: int
+    lenses: list[Optional[Lens]] = field(hash=False, default_factory=list)
+    lens_index_lookup: dict[str, Lens] = field(hash=False, default_factory=dict)
+
+    @property
+    def focusing_power(self) -> int:
+        output = 0
+        box_num = self.id + 1
+        lenses = [lens for lens in self.lenses if lens and not lens.deleted]
+        for i, lens in enumerate(lenses):
+            lens_num = i + 1
+            output += box_num * lens_num * lens.focus_length
+
+        return output
+
+    def remove_lens(self, label: str) -> None:
+        if label in self.lens_index_lookup:
+            self.lens_index_lookup[label].deleted = True
+            del self.lens_index_lookup[label]
+
+    def set_lens(self, label: str, value) -> None:
+        if label in self.lens_index_lookup:
+            lens = self.lens_index_lookup[label]
+            lens.focus_length = value
+        else:
+            lens = Lens(label, value)
+            self.lenses.append(lens)
+            self.lens_index_lookup[label] = lens
+
+
+@dataclass
+class Day15PartBSolver:
+    lines: list[str]
+
+    @property
+    def solution(self) -> int:
+        for op in self.operations:
+            self.do_operation(op)
+        return sum(box.focusing_power for box in self.boxes)
+
+    @cached_property
+    def boxes(self) -> list[Box]:
+        return [Box(i, []) for i in range(256)]
+
+    @cached_property
+    def operations(self) -> list[Minus | Equal]:
+        output = list[Minus | Equal]()
+        for line in self.lines:
+            if line[-1] == "-":
+                output.append(Minus(line[:-1]))
+            else:
+                label, val = line.split("=")
+                output.append(Equal(label, int(val)))
+        return output
+
+    def do_operation(self, op: Minus | Equal) -> None:
+        box_id = hash_it(op.label)
+        box = self.boxes[box_id]
+
+        match op:
+            case Minus(label):
+                box.remove_lens(label)
+            case Equal(label, val):
+                box.set_lens(label, val)
+
+
+def solve(input: str) -> int:
+    data = Parser.parse(input)
+    solver = Day15PartBSolver(data)
+
+    return solver.solution
+
+
+def get_solution() -> int:
+    with open("aoc_2023/day_15/input.txt", "r") as f:
+        input = f.read()
+    return solve(input)
+
+
+if __name__ == "__main__":
+    print(get_solution())

aoc_2023/day_15/common.py

@@ -0,0 +1,7 @@
+def hash_it(line: str) -> int:
+    output = 0
+    for char in line:
+        output += ord(char)
+        output *= 17
+        output %= 256
+    return output

aoc_2023/day_15/parser.py

@@ -0,0 +1,4 @@
+class Parser:
+    @staticmethod
+    def parse(input: str) -> list[str]:
+        return input.strip().split(",")

tests/test_day_15/test_a.py

@@ -0,0 +1,13 @@
+from aoc_2023.day_15.a import get_solution, solve
+from aoc_2023.day_15.from_prompt import (
+    SAMPLE_DATA,
+    SAMPLE_SOLUTION_A,
+)
+
+
+def test_solve():
+    assert solve(SAMPLE_DATA) == SAMPLE_SOLUTION_A
+
+
+def test_my_solution():
+    assert get_solution() == 517015

tests/test_day_15/test_b.py

@@ -0,0 +1,10 @@
+from aoc_2023.day_15.b import get_solution, solve
+from aoc_2023.day_15.from_prompt import SAMPLE_DATA, SAMPLE_SOLUTION_B
+
+
+def test_solve():
+    assert solve(SAMPLE_DATA) == SAMPLE_SOLUTION_B
+
+
+def test_my_solution():
+    assert get_solution() == 286104

tests/test_day_15/test_common.py

@@ -0,0 +1,6 @@
+from aoc_2023.day_15.common import hash_it
+from aoc_2023.day_15.from_prompt import HASH, HASH_HASHED
+
+
+def test_hash():
+    assert hash_it(HASH) == HASH_HASHED