Scala3

def countDyn(a: List[Char], b: List[Int]): Long =
    // Simple dynamic programming approach
    // We fill a table T, where
    //  T[ ai, bi ] -> number of ways to place b[bi..] in a[ai..]
    //  T[ ai, bi ] = 0 if an-ai >= b[bi..].sum + bn-bi
    //  T[ ai, bi ] = 1 if bi == b.size - 1 && ai == a.size - b[bi] - 1
    //  T[ ai, bi ] = 
    //   (place) T [ ai + b[bi], bi + 1]   if ? or # 
    //   (skip)  T [ ai + 1, bi ]          if ? or .
    // 
    def t(ai: Int, bi: Int, tbl: Map[(Int, Int), Long]): Long =
        if ai >= a.size then
            if bi >= b.size then 1L else 0L 
        else
            val place = Option.when(
                bi < b.size && // need to have piece left
                ai + b(bi) <= a.size && // piece needs to fit
                a.slice(ai, ai + b(bi)).forall(_ != '.') && // must be able to put piece there
                (ai + b(bi) == a.size || a(ai + b(bi)) != '#') // piece needs to actually end
            )((ai + b(bi) + 1, bi + 1)).flatMap(tbl.get).getOrElse(0L)
            val skip = Option.when(a(ai) != '#')((ai + 1, bi)).flatMap(tbl.get).getOrElse(0L)
            place + skip

    @tailrec def go(ai: Int, tbl: Map[(Int, Int), Long]): Long =
        if ai == 0 then t(ai, 0, tbl) else go(ai - 1, tbl ++ b.indices.inclusive.map(bi => (ai, bi) -> t(ai, bi, tbl)).toMap)

    go(a.indices.inclusive.last + 1, Map())

def countLinePossibilities(repeat: Int)(a: String): Long =
    a match
        case s"$pattern $counts" => 
            val p2 = List.fill(repeat)(pattern).mkString("?")
            val c2 = List.fill(repeat)(counts).mkString(",")
            countDyn(p2.toList, c2.split(",").map(_.toInt).toList)
        case _ => 0L


def task1(a: List[String]): Long = a.map(countLinePossibilities(1)).sum
def task2(a: List[String]): Long = a.map(countLinePossibilities(5)).sum

(Edit: fixed mangling of &<)