2024 day 8 parts 1 and 2

README.md

@@ -15,7 +15,7 @@
 - 2021 - ★★★★★ ★★★★★ ★★★★★ ★★★
 - 2022 - ★★★★★ ★★★★★ ★★★★★ ★☆
 - 2023 - ★★★★★ ★★★★★ ★★★★★ ★★★☆
-- 2024 - ★★★★★ ★★
+- 2024 - ★★★★★ ★★★
 
 ## How to use
 

src/year2024/day08a.py

@@ -0,0 +1,39 @@
+"""2024 - Day 8 Part 1: Resonant Collinearity"""
+
+from collections import defaultdict
+from itertools import combinations
+
+
+def solve(task: str) -> int:
+    data = task.split("\n")
+
+    rows = len(data)
+    cols = len(data[0])
+
+    antennas: dict[str, list[tuple[int, int]]] = defaultdict(list)
+
+    for r, row in enumerate(data):
+        for c, item in enumerate(row):
+            if item not in {".", "#"}:
+                antennas[item].append((r, c))
+
+    ants: set[tuple[int, int]] = set()
+
+    for k, v in antennas.items():
+        for a1, a2 in combinations(antennas[k], 2):
+            r1, c1 = a1
+            r2, c2 = a2
+
+            dr = r1 - r2
+            dc = c1 - c2
+
+            for ar, ac in (
+                (r1 - dr, c1 - dc),
+                (r1 + dr, c1 + dc),
+                (r2 - dr, c2 - dc),
+                (r2 + dr, c2 + dc),
+            ):
+                if 0 <= ar < rows and 0 <= ac < cols and data[ar][ac] != k:
+                    ants.add((ar, ac))
+
+    return len(ants)

src/year2024/day08b.py

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+"""2024 - Day 8 Part 2: Resonant Collinearity"""
+
+from collections import defaultdict
+from itertools import combinations
+
+
+def solve(task: str) -> int:
+    data = task.split("\n")
+
+    rows = len(data)
+    cols = len(data[0])
+
+    antennas: dict[str, list[tuple[int, int]]] = defaultdict(list)
+
+    for r, row in enumerate(data):
+        for c, item in enumerate(row):
+            if item not in {".", "#"}:
+                antennas[item].append((r, c))
+
+    ants: set[tuple[int, int]] = set()
+
+    for k, v in antennas.items():
+        for a1, a2 in combinations(antennas[k], 2):
+            r1, c1 = a1
+            r2, c2 = a2
+
+            dr = r1 - r2
+            dc = c1 - c2
+
+            ar1 = r1 - dr
+            ac1 = c1 - dc
+
+            ar2 = r1 + dr
+            ac2 = c1 + dc
+
+            ar3 = r2 - dr
+            ac3 = c2 - dc
+
+            ar4 = r2 + dr
+            ac4 = c2 + dc
+
+            while 0 <= ar1 < rows and 0 <= ac1 < cols:
+                ants.add((ar1, ac1))
+                ar1 -= dr
+                ac1 -= dc
+
+            while 0 <= ar2 < rows and 0 <= ac2 < cols:
+                ants.add((ar2, ac2))
+                ar2 += dr
+                ac2 += dc
+
+            while 0 <= ar3 < rows and 0 <= ac3 < cols:
+                ants.add((ar3, ac3))
+                ar3 -= dr
+                ac3 -= dc
+
+            while 0 <= ar4 < rows and 0 <= ac4 < cols:
+                ants.add((ar4, ac4))
+                ar4 += dr
+                ac4 += dc
+
+    return len(ants)

tests/src/year2024/test_day08a.py

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+"""2024 - Day 8 Part 1: Resonant Collinearity"""
+
+from textwrap import dedent
+
+from src.year2024.day08a import solve
+
+
+def test_solve():
+    task = dedent(
+        """
+        ......#....#
+        ...#....0...
+        ....#0....#.
+        ..#....0....
+        ....0....#..
+        .#....A.....
+        ...#........
+        #......#....
+        ........A...
+        .........A..
+        ..........#.
+        ..........#.
+        """
+    ).strip()
+    assert solve(task) == 14

tests/src/year2024/test_day08b.py

@@ -0,0 +1,25 @@
+"""2024 - Day 8 Part 2: Resonant Collinearity"""
+
+from textwrap import dedent
+
+from src.year2024.day08b import solve
+
+
+def test_solve():
+    task = dedent(
+        """
+        ##....#....#
+        .#.#....0...
+        ..#.#0....#.
+        ..##...0....
+        ....0....#..
+        .#...#A....#
+        ...#..#.....
+        #....#.#....
+        ..#.....A...
+        ....#....A..
+        .#........#.
+        ...#......##
+        """
+    ).strip()
+    assert solve(task) == 34