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Flattening a list of lists to a set with exceptions in scala


Flattening a list of lists to a set with exceptions in scala

By : rdina
Date : November 22 2020, 10:54 AM
may help you . This feels like a peculiar problem and I am very new to Scala, so I don't know how to ask the right questions in order to get progress on this problem. , Try this
code :
val data = List(List(1, 2, 3, 4), List(1, 2, 2, 3, 4), List(1, 2, 3, 3, 3, 4), List(1, 2, 3, 4), List(2, 3, 4))

val map = data.map(_.groupBy(identity)).foldLeft(Map[Int, List[Int]]()) {
   case (r, c) => r ++ c.map {
       case (k, v) => k -> (if (v.size > r.getOrElse(k, List()).size) v else r(k))
}
}.values.flatten                               
//> map  : Iterable[Int] = List(2, 2, 4, 1, 3, 3, 3)
data.flatMap(_.groupBy(identity)).groupBy(_._1).mapValues(_.sortBy(_._2.size).reverse(0)._2).values.flatten
//> res0: Iterable[Int] = List(2, 2, 4, 1, 3, 3, 3)


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Flattening nested java lists in Scala

Flattening nested java lists in Scala


By : BebekBeziPasta
Date : March 29 2020, 07:55 AM
hope this fix your issue I am working in Scala with java libraries. One of these libraries returns a list of lists. I want to flatten the list. , You need to call .asScala on every inner list :
code :
scala> parentList.asScala.map(_.asScala)
res0: scala.collection.mutable.Buffer[scala.collection.mutable.Buffer[Int]] = ArrayBuffer()

scala> parentList.asScala.map(_.asScala).flatten
res1: scala.collection.mutable.Buffer[Int] = ArrayBuffer()
scala> parentList.asScala.flatMap(_.asScala)
res2: scala.collection.mutable.Buffer[Int] = ArrayBuffer()
flattening list of lists in Scala with out using flatten method giving bad result

flattening list of lists in Scala with out using flatten method giving bad result


By : user3524592
Date : March 29 2020, 07:55 AM
To fix this issue I tried to flatten the list of lists using the below code. When I put it on paper, it should work but I think I misinterpreted or am ignorant of how lists work. Could any one tell me where i went wrong. , You can actually pattern match deep into the structure:
code :
def flatten[T](xss: List[List[T]]): List[T] = xss match {
   case Nil => Nil
   case Nil :: tail => flatten(tail)
   case (innerHead :: innerTail) :: tail => innerHead :: flatten(innerTail :: tail)
}
Flattening list of lists

Flattening list of lists


By : Carlos Laso
Date : March 29 2020, 07:55 AM
it fixes the issue As long as your lists can't be nested more than one deep, you could do:
code :
def flatten(lst):
    for el in lst:
        if isinstance(el, list):
            yield from el
        else:
            yield el
a = [['a'], 'b', 'c', 'd', 'e']
flat_a = flatten(a)  # not a list, but an iterator that returns flat values
flat_a_as_lst = list(flat_a)  # actually a list
Flattening a list of lists within a map

Flattening a list of lists within a map


By : user2746113
Date : March 29 2020, 07:55 AM
I wish this helpful for you I have a stream of orders (the source being a list of orders). Each order has a Customer, and a list of OrderLine. , You can simply use Collectors.toMap.
Something like
code :
    orders
        .stream()
        .collect(Collectors
                .toMap(Order::getCustomer
                        , Order::getOrderLines
                        , (v1, v2) -> { List<OrderLine> temp = new ArrayList<>(v1); 
                                        temp.addAll(v2); 
                                        return temp;});
Flattening a List of Lists

Flattening a List of Lists


By : ravindranath
Date : March 29 2020, 07:55 AM
help you fix your problem This is a (weird) fold
This is a generalized folding procedure. In Lisps, lists are represented by cons cells and the empty list, where each (proper) list is either the empty list (), or a cons cell whose car is an element of the list and whose cdr is the rest of the list. E.g., a list (1 2 3 4 5) can be produced by
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