45 lines
1.2 KiB
Python
45 lines
1.2 KiB
Python
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with open("input.txt") as f:
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lines = f.read().splitlines()
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freqs = [int(line) for line in lines]
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print("Part 1:", sum(freqs))
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## what follows is a O(n log n) solution using modulos to avoid cycling manually.
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## personally i just did it in elixir with Stream.cycle()...
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from itertools import accumulate
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sums = [0] + list(accumulate(freqs))
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seen = set()
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# check first cycle
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for s in sums:
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if s in seen:
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ans2 = s
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seen.add(s)
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# check if last element is 0 (can't do mod 0)
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tail = sums[-1]
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if tail == 0:
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ans2 = 0
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# calculate mapping of all mods and indexes
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sums = sums[:-1] # the last sum is part of the next iteration -- we start at 0
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from collections import defaultdict
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mods = defaultdict(list)
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for i, s in enumerate(sums):
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mods[s % tail].append((i,s))
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mini, mind, minf = None, None, None
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for m in mods.values():
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ss = list(sorted(m, key = lambda t: t[1])) # sort by second element of tuple
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for i in range(1,len(ss)):
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diff = ss[i][1] - ss[i-1][1]
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index = ss[i-1][0] if tail > 0 else ss[i][0]
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freq = ss[i][1] if tail > 0 else ss[i-1][1]
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if mind is None or diff < mind or (diff == mind and index < mini):
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mini = index
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mind = diff
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minf = freq
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ans2 = minf
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print("Part 2:", ans2)
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