dsf

def decode(tree: CodeTree, bits: List[Bit]): List[Char] = {
    def decodeAcc(t: CodeTree, bs: List[Bit], acc: List[Char]): List[Char] = t match {
      case Leaf( c, w ) =>
        if( bs.isEmpty )
          List(c)
        else
          decodeAcc( tree, bs, acc:::List(c) )
      case Fork( l,r,c,w ) =>
        if ( bs.head == 0 ) decodeAcc( l, bs.tail, acc )
        else decodeAcc( r, bs.tail, acc )
    }
    decodeAcc( tree, bits, List() )
  }