aoc2023/Day1.scala

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package aoc.day1
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import aoc._
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// Part 1
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def literalDigits(s: String) =
s.toSeq.filter(_.isDigit).map(v => (v - '0').toInt)
def getValue(toDigits: String => Seq[Int])(s: String): Int =
val digits = toDigits(s)
digits.head * 10 + digits.last
def getSum(toDigits: String => Seq[Int]) =
val values =
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lines.map(getValue(toDigits))
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println(values.sum)
// Part 2
val englishDigits =
Seq("one", "two", "three", "four", "five", "six", "seven", "eight", "nine")
def literalOrEnglishDigits(s: String) =
@scala.annotation.tailrec
def loop(idx: Int, accum: Seq[Int]): Seq[Int] =
if idx < 0 then accum
else if s(idx).isDigit then loop(idx - 1, (s(idx) - '0').toInt +: accum)
else
val toMatch = s.slice(idx, idx + 5 /* enough to match english */ )
val digit = englishDigits.indexWhere(toMatch.startsWith _)
val nAccum = if digit == -1 then accum else (digit + 1) +: accum
loop(idx - 1, nAccum)
loop(s.length() - 1, Seq.empty)
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@main def Day1(part: Int) = part match
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case 1 => getSum(literalDigits)
case 2 => getSum(literalOrEnglishDigits)