45 lines
1.3 KiB
Nim
45 lines
1.3 KiB
Nim
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# Copyright 2021 Christian Ulrich
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# usage: ./part2 < input
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import algorithm
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import sequtils
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import strutils
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const Days = 256
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proc predictLanternfishCount(): uint64 =
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let timers = readLine(stdin).split(',').mapIt(uint8(parseUint(it)))
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var counters: array[9, uint64]
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for timer in timers:
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if timer > 8:
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raise newException(ValueError, "invalid timer")
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counters[timer].inc()
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for day in 0 ..< Days:
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counters.rotateLeft(1)
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counters[6] += counters[8]
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result = counters.foldl(a + b, 0'u64)
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proc main(): int =
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try:
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echo predictLanternfishCount()
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except Exception as error:
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echo error.msg
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result = -1
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when isMainModule:
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quit(main())
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