Solve 2020 day 10

2020/10_jolts.py

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+#!/usr/bin/env python3
+import sys
+from functools import lru_cache
+from itertools import combinations
+
+def diffs(adapters):
+    prev = 0
+    for jolts in adapters:
+        yield jolts - prev
+        prev = jolts
+    yield 3
+
+def mul_diffs(adapters):
+    d = list(diffs(adapters))
+    return d.count(1) * d.count(3)
+
+def arrangements(adapters):
+    graph = {}
+    for a, b in combinations([0] + adapters, 2):
+        if b - a <= 3:
+            graph.setdefault(a, []).append(b)
+
+    @lru_cache(maxsize=None)
+    def walk(node):
+        if node == adapters[-1]:
+            return 1
+        elif not graph[node]:
+            return 0
+        return sum(map(walk, graph[node]))
+
+    return walk(0)
+
+adapters = sorted(map(int, sys.stdin))
+print(mul_diffs(adapters))
+print(arrangements(adapters))

2020/input/10

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