#!/usr/bin/python3 import collections import itertools type Antennas = defaultdict[str, list[complex]] def main() -> None: with open("input", "r") as f: data = [x.rstrip() for x in f.readlines()] w, h = len(data[0]), len(data) antennas: Antennas = collections.defaultdict(list) antinodes: set[complex] = set() for y, row in enumerate(data): for x, ch in enumerate(row): if ch != '.': antennas[ch].append(complex(x, y)) for coords in antennas.values(): for a, b in itertools.combinations(coords, 2): v⃗ = a - b u⃗ = b - a # START PART 1 antinodes.add(a + u⃗*2) antinodes.add(b + v⃗*2) # END PART 1 START PART 2 for i in range(1, max(w, h)): antinodes.add(a + u⃗*i) antinodes.add(b + v⃗*i) # END PART 2 print(sum(0 <= x.real < w and 0 <= x.imag < h for x in antinodes)) if __name__ == "__main__": main()