37 lines
1.1 KiB
Nim
37 lines
1.1 KiB
Nim
import streams, sequtils, strutils
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proc part1*(s: Stream): int =
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let schedule = toSeq(s.lines)
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let departure = schedule[0].parseInt
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var ss = schedule[1].split(",").filterIt(it != "x" and it != "").map(parseInt)
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var mn = (0, departure*2)
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for n in ss:
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let q = n * ((departure div n) + 1)
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if q < mn[1]:
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mn = (n, q)
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mn[0] * (mn[1] - departure)
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import tables
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proc part2*(s: Stream): int =
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var ss = toSeq(s.lines)[1].split(",").filterIt(it != "")
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var bb = initTable[int, int]()
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for n in 0..<ss.len:
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if ss[n] == "x": continue
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bb[n] = ss[n].parseInt
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let incr = bb[0]
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var i = 0
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while true:
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# TODO: this takes too long, need to learn the math?
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# maybe between each bus there is a regular period of these "coincidences" and we can reduce along those?
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for j in 1..<ss.len:
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if bb.contains j:
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let d = i+j
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let b = bb[j]
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let nn = b * (d div b)
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# echo ("checking", i, j, b, d, nn)
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if d != nn: break
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# echo ("good", j)
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if j == ss.len-1: return i
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else: continue
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inc i, incr
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