Add Day 8: Part 2

Author: juergenhoetzel

README.md

@@ -11,4 +11,4 @@
 | [Day 5: Print Queue](https://adventofcode.com/2024/day/5)           | ✅     | ✅     | [day5.py](aoc/day5.py) |
 | [Day 6: Guard Gallivant](https://adventofcode.com/2024/day/6)       | ✅     | ✅     | [day6.py](aoc/day6.py) |
 | [Day 7: Bridge Repair](https://adventofcode.com/2024/day/7)         | ✅     | ✅     | [day7.py](aoc/day7.py) |
-| [Day 8: Resonant Collinearity](https://adventofcode.com/2024/day/8) | ✅     | ❌     | [day8.py](aoc/day8.py) |
+| [Day 8: Resonant Collinearity](https://adventofcode.com/2024/day/8) | ✅     | ✅     | [day8.py](aoc/day8.py) |

aoc/day8.py

@@ -19,7 +19,7 @@ def parse_input(lines: list[str]) -> AntennaMap:
     return AntennaMap(len(lines), len(lines[0]), antennamap)
 
 
-def positions(am: AntennaMap) -> set[tuple[int, int]]:
+def positions(am: AntennaMap, mul=1) -> set[tuple[int, int]]:
     anodes_pos = set()
 
     def is_in_field(pos):
@@ -29,7 +29,9 @@ def is_in_field(pos):
     for _, positions in am.positions.items():
         for (y1, x1), (y2, x2) in combinations(positions, 2):
             anodes_pos |= {
-                pos for pos in [(y1 + (y1 - y2), x1 + (x1 - x2)), (y2 + (y2 - y1), x2 + (x2 - x1))] if is_in_field(pos)
+                pos
+                for pos in [(y1 + (y1 - y2) * mul, x1 + (x1 - x2) * mul), (y2 + (y2 - y1) * mul, x2 + (x2 - x1) * mul)]
+                if is_in_field(pos)
             }
     return anodes_pos
 
@@ -38,9 +40,19 @@ def part1(am: AntennaMap) -> int:
     return len(positions(am))
 
 
+def part2(am: AntennaMap) -> int:
+    anodes = set()
+    for i in range(1, max(am.cols, am.rows)):
+        anodes |= positions(am, i)
+    for v in am.positions.values():
+        anodes |= v
+    return len(anodes)
+
+
 def main():
     lines = parse_input(Path(sys.argv[1]).read_text().splitlines())
     print(f"Part 1: {part1(lines)}")
+    print(f"Part 2: {part2(lines)}")
 
 
 if __name__ == "__main__":

test/test_day8.py

@@ -1,4 +1,4 @@
-from aoc.day8 import parse_input, part1
+from aoc.day8 import parse_input, part1, part2
 
 TEST_INPUT = """............
 ........0...
@@ -17,3 +17,7 @@
 
 def test_part1():
     assert part1(parse_input(TEST_INPUT)) == 14
+
+
+def test_part2():
+    assert part2(parse_input(TEST_INPUT)) == 34