blob: 9dba99e3536000bc8448c7633216c35565ecc55a (
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lines = []
with open("input") as f:
for line in f:
lines.append(line.strip())
antennas: dict[str, list[tuple[int, int]]] = {}
for row_idx, line in enumerate(lines):
for col_idx, char in enumerate(line):
if char != ".":
if char not in antennas:
antennas[char] = []
antennas[char].append((row_idx, col_idx))
row_count = len(lines)
col_count = len(lines[0])
antinodes: set[tuple[int, int]] = set()
for antenna_list in antennas.values():
for idx, antenna1 in enumerate(antenna_list):
for antenna2 in antenna_list[idx + 1:]:
row_diff = antenna2[0] - antenna1[0]
col_diff = antenna2[1] - antenna1[1]
pos1 = (antenna1[0] - row_diff, antenna1[1] - col_diff)
pos2 = (antenna2[0] + row_diff, antenna2[1] + col_diff)
if 0 <= pos1[0] < row_count and 0 <= pos1[1] < col_count:
antinodes.add(pos1)
if 0 <= pos2[0] < row_count and 0 <= pos2[1] < col_count:
antinodes.add(pos2)
print(len(antinodes))
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