Add Day2

Author: juergenhoetzel

Diff for: README.md

@@ -2,8 +2,9 @@
 
 ## Solutions
 
-| Advent of Code Page                                       | Part 1 | Part 2 | Day                  |
-|-----------------------------------------------------------|--------|--------|----------------------|
+| Advent of Code Page                                              | Part 1 | Part 2 | Day                    |
+|------------------------------------------------------------------|--------|--------|------------------------|
 | [Day 1: Historian Hysteria](https://adventofcode.com/2024/day/1) | ✅     | ✅     | [day1.py](aoc/day1.py) |
+| [Day 2: Red-Nosed Reports](https://adventofcode.com/2024/day/2)  | ✅     | ✅     | [day2.py](aoc/day2.py) |
 
 

Diff for: aoc/day2.py

@@ -0,0 +1,43 @@
+import sys
+from pathlib import Path
+
+
+def load_reports(report_path: Path) -> list[list[int]]:
+    return [[int(x) for x in line.split()] for line in report_path.read_text().splitlines() if line]
+
+
+def is_safe(levels: list[int]) -> bool:
+    differences = [(j - i) for (i, j) in zip(levels, levels[1:])]
+    return all([1 <= d <= 3 for d in differences]) or all([-3 <= d <= -1 for d in differences])
+
+
+def unsafe_level_index(levels: list[int], min_level=1, max_level=3) -> int | None:
+    for i in range(len(levels) - 1):
+        if not min_level <= (levels[i + 1] - levels[i]) <= max_level:
+            return i
+
+
+def is_safe_dampened(levels: list[int]) -> bool:
+    for ranges in [(1, 3), (-3, -1)]:
+        i = unsafe_level_index(levels, *ranges)
+        if i is None:
+            return True
+        elif unsafe_level_index(levels[:i] + levels[i + 1 :], *ranges) is None:
+            return True
+        elif unsafe_level_index(levels[: i + 1] + levels[i + 2 :], *ranges) is None:
+            return True
+    return False
+
+
+def count_report_safe(report_path: Path, is_safe_fn=is_safe) -> int:
+    reports = load_reports(report_path)
+    return sum([is_safe_fn(levels) for levels in reports])
+
+
+def main():
+    print(count_report_safe(Path(sys.argv[1])))
+    print(count_report_safe(Path(sys.argv[1]), is_safe_dampened))
+
+
+if __name__ == "__main__":
+    main()

Diff for: test/test_day2.py

@@ -0,0 +1,47 @@
+from pathlib import Path
+
+import pytest
+
+from aoc.day2 import count_report_safe, is_safe, is_safe_dampened
+
+TESTDATA = """
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9
+"""
+
+
+def test_day2_is_safe():
+    assert is_safe([7, 6, 4, 2, 1])
+    assert not is_safe([1, 2, 7, 8, 9])
+    assert not is_safe([9, 7, 6, 2, 1])
+    assert not is_safe([1, 3, 2, 4, 5])
+    assert not is_safe([8, 6, 4, 4, 1])
+    assert is_safe([1, 3, 6, 7, 9])
+
+
+@pytest.fixture(scope="session")
+def input_path(tmpdir_factory):
+    p = Path(tmpdir_factory.mktemp("data")) / "input.txt"
+    p.write_text(TESTDATA)
+    return p
+
+
+def test_day2_count_reports(input_path):
+    assert count_report_safe(input_path) == 2
+
+
+def test_day2_is_dampened_safe():
+    assert is_safe_dampened([7, 6, 4, 2, 1])
+    assert not is_safe_dampened([1, 2, 7, 8, 9])
+    assert not is_safe_dampened([9, 7, 6, 2, 1])
+    assert is_safe_dampened([1, 3, 2, 4, 5])
+    assert is_safe_dampened([8, 6, 4, 4, 1])
+    assert is_safe_dampened([1, 3, 6, 7, 9])
+
+
+def test_day2_count_dampened_reports(input_path):
+    assert count_report_safe(input_path, is_safe_fn=is_safe_dampened) == 4