feat: add solution 2025/04

data/example/2025/04.txt

@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.

src/solution/year_2025/day_04.py

@@ -0,0 +1,58 @@
+from typing import Any
+
+dirs = [(0, 1), (0, -1), (1, 0), (-1, 0), (1, 1), (-1, -1), (-1, 1), (1, -1)]
+
+
+def _count_and_remove_rolls(diagram: list[list[str]], replace: bool = False) -> int:
+    c = 0
+    for i, line in enumerate(diagram):
+        for j, cell in enumerate(line):
+            if cell != "@":
+                continue
+
+            n = 0
+            for di, dj in dirs:
+                ni, nj = (i + di, j + dj)
+
+                if (
+                    (0 <= ni < len(diagram))
+                    and (0 <= nj < len(line))
+                    and diagram[ni][nj] == "@"
+                ):
+                    n += 1
+
+            if n >= 4:
+                continue
+
+            c += 1
+            if replace:
+                diagram[i][j] = "."
+
+    return c
+
+
+def part_1(input_data: str) -> Any:
+    diagram = [list(x) for x in input_data.splitlines()]
+    return _count_and_remove_rolls(diagram)
+
+
+def part_2(input_data: str) -> Any:
+    diagram = [list(x) for x in input_data.splitlines()]
+
+    c = 0
+    while True:
+        n = _count_and_remove_rolls(diagram, True)
+        if n == 0:
+            break
+
+        c += n
+
+    return c
+
+
+def test_part_1(example_data):
+    assert part_1(example_data) == 13
+
+
+def test_part_2(example_data):
+    assert part_2(example_data) == 43