gistfile1.scala

Task(typeTask:String, id:Int, parentProject:Int price:Float)

notice "p" means project 
task for "t"
there can be n number of tasks below project
and parent of project id will be always zero

the list is ordered based on id field

List(
new Task("p", 1, 0, 0.0),
    new Task("t", 10, 1, 1.1),
    new Task("t", 11, 1, 1.1),
        
new Task("p", 20, 0, 0.0),
    new Task("t", 21, 2, 2.1),
    new Task("t", 22, 2, 2.1),
    new Task("t", 23, 2, 2.1)
)

I want to add up the price of tasks into Projects' price
so output should be

notice "2.2" value change in first item
and 6.3 change in 4th item

List(
new Task("p", 1, 0, 2.2),
    new Task("t", 10, 1, 1.1),
    new Task("t", 11, 1, 1.1),
        
new Task("p", 20, 0, 6.3),
    new Task("t", 21, 2, 2.1),
    new Task("t", 22, 2, 2.1),
    new Task("t", 23, 2, 2.1)
)

sealed trait Task {
def id: Int
def price: Float
}

case class SimpleTask(id: Int, price: Float) extends Task
case class ProjectTask(id: Int, subTasks: List[Task]) extends Task {
def price: Float = subTasks.reduceLeft(_.price + _.price)
}