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1 files changed, 36 insertions, 0 deletions

diff --git a/2020/10/puzzle-2.py b/2020/10/puzzle-2.py
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+++ b/2020/10/puzzle-2.py
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+#!/usr/bin/env python3
+
+from typing import List
+
+adaptors: list[str]
+
+
+def combos(i: int, counts: dict[int, dict[int, int]] = {}) -> int:
+	if i == len(adaptors) - 1:
+		return 1
+	if i in counts:
+		return counts[i]
+
+	ans = 0
+	for j in range(i + 1, len(adaptors)):
+		if adaptors[j] - adaptors[i] <= 3:
+			ans += combos(j, counts)
+
+	counts[i] = ans
+	return ans
+
+
+def main() -> None:
+	global adaptors
+	with open("input", "r") as f:
+		adaptors = list(map(int, f.readlines()))
+
+	adaptors.append(0)
+	adaptors.sort()
+	adaptors.append(max(adaptors) + 3)
+
+	print(combos(0))
+
+
+if __name__ == "__main__":
+	main()