feat: 2025 day04

Author: fabiogallotti

.pre-commit-config.yaml

@@ -1,7 +1,6 @@
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.14.7
+    rev: v0.14.8
     hooks:
-      - id: ruff
-        args: [--fix]
+      - id: ruff-check
       - id: ruff-format

README.md

@@ -7,7 +7,7 @@
 | 01 | [✓][012015] |             |             |             | [✓][012019] | [✓][012020] | [✓][012021] | [✓][012022] | [✓][012023] | [✓][012024] | [✓][012025] |
 | 02 | [✓][022015] |             |             |             | [✓][022019] | [✓][022020] | [✓][022021] | [✓][022022] | [✓][022023] | [✓][022024] | [✓][022025] |
 | 03 | [✓][032015] |             |             |             | [✓][032019] | [✓][032020] | [✓][032021] | [✓][032022] | [✓][032023] | [✓][032024] | [✓][032025] |
-| 04 | [✓][042015] |             |             |             | [✓][042019] | [✓][042020] | [✓][042021] | [✓][042022] | [✓][042023] | [✓][042024] |             |
+| 04 | [✓][042015] |             |             |             | [✓][042019] | [✓][042020] | [✓][042021] | [✓][042022] | [✓][042023] | [✓][042024] | [✓][042025] |
 | 05 | [✓][052015] |             |             |             |             | [✓][052020] |             | [✓][052022] | [✓][052023] | [✓][052024] | [✓][052025] |
 | 06 | [✓][062015] |             |             |             |             | [✓][062020] |             | [✓][062022] | [✓][062023] | [✓][062024] |             |
 | 07 | [✓][072015] |             |             |             |             | [✓][072020] |             | [✓][072022] | [✓][072023] | [✓][072024] |             |
@@ -132,7 +132,7 @@
 [012025]: https://github.com/fabiogallotti/adventofcode/tree/master/src/year2025/day01
 [022025]: https://github.com/fabiogallotti/adventofcode/tree/master/src/year2025/day02
 [032025]: https://github.com/fabiogallotti/adventofcode/tree/master/src/year2025/day03
-
+[042025]: https://github.com/fabiogallotti/adventofcode/tree/master/src/year2025/day04
 [052025]: https://github.com/fabiogallotti/adventofcode/tree/master/src/year2025/day05
 
 ## To run an exercise ##

pyproject.toml

@@ -14,7 +14,7 @@ description = ""
 readme = "README.md"
 
 [dependency-groups]
-dev = ["pre-commit>=4.5.0", "pytest>=9.0.1", "ruff>=0.14.7"]
+dev = ["pre-commit>=4.5.0", "pytest>=9.0.1", "ruff>=0.14.8"]
 
 [build-system]
 requires = ["pdm-backend"]

src/year2025/day04/exercises.py

@@ -0,0 +1,10 @@
+from functions.read_input import read_input
+from inputs.path import PATH
+
+from .functions import part_1, part_2
+
+data = read_input(f"{PATH}/2025/day04.txt")
+
+print(f"First part: {part_1(data)}")
+
+print(f"Second part: {part_2(data)}")

src/year2025/day04/functions.py

@@ -0,0 +1,73 @@
+from enum import Enum
+
+from pydantic import BaseModel
+
+
+class Position(BaseModel):
+    x: int
+    y: int
+
+    def __hash__(self):
+        return hash(str(self.x) + str(self.y))
+
+
+class Direction(Enum):
+    UP = (-1, 0)
+    RIGHT = (0, 1)
+    DOWN = (1, 0)
+    LEFT = (0, -1)
+    UP_RIGHT = (-1, 1)
+    DOWN_RIGHT = (1, 1)
+    DOWN_LEFT = (1, -1)
+    UP_LEFT = (-1, -1)
+
+
+def preprocessing(data):
+    paper = set()
+    for i in range(len(data)):
+        for j in range(len(data[0])):
+            elem = data[i][j]
+            if elem == "@":
+                paper.add(Position(x=i, y=j))
+
+    return paper
+
+
+def part_1(data):
+    directions = list(Direction)
+    paper = preprocessing(data)
+    total = 0
+
+    for elem in paper:
+        count = 0
+        for direction in directions:
+            dx, dy = direction.value
+            next_pos = Position(x=elem.x + dx, y=elem.y + dy)
+            if next_pos in paper:
+                count += 1
+        if count < 4:
+            total += 1
+    return total
+
+
+def part_2(data):
+    directions = list(Direction)
+    paper = preprocessing(data)
+    total = 0
+
+    while True:
+        to_remove = set()
+        for elem in paper:
+            count = 0
+            for direction in directions:
+                dx, dy = direction.value
+                next_pos = Position(x=elem.x + dx, y=elem.y + dy)
+                if next_pos in paper:
+                    count += 1
+            if count < 4:
+                total += 1
+                to_remove.add(elem)
+        if not to_remove:
+            break
+        paper -= to_remove
+    return total

tests/2025/test_2025day04.py

@@ -0,0 +1,22 @@
+from year2025.day04.functions import part_1, part_2
+
+EXAMPLE_1 = [
+    "..@@.@@@@.",
+    "@@@.@.@.@@",
+    "@@@@@.@.@@",
+    "@.@@@@..@.",
+    "@@.@@@@.@@",
+    ".@@@@@@@.@",
+    ".@.@.@.@@@",
+    "@.@@@.@@@@",
+    ".@@@@@@@@.",
+    "@.@.@@@.@.",
+]
+
+
+def test_part_1():
+    assert part_1(EXAMPLE_1) == 13
+
+
+def test_part_2():
+    assert part_2(EXAMPLE_1) == 43