Здравейте, опитвам се да напиша прост алгоритъм за изкачване на хълм в scala.
Имам State
и HillClimbing
, които са черти. Определям ги като конкретни класове, когато ги прилагам към проблема Graph
.
В GraphHillClimbing
получавам две грешки. Това е така, защото използвам GraphState
вместо State
(забележете, че GraphState
също е State
).
Как мога да разреша това?
trait State {
val loc = 0
def neighbours: List[State]
def get_loc():Int = return loc
}
class GraphState(loc:Int, g: Map[Int, List[Int]]) extends State {
def neighbours():List[GraphState] =
{
def neighboursAcc(l:List[Int], acc:List[GraphState], g:Map[Int, List[Int]]):List[GraphState] =
{
if(l.isEmpty) acc
else {
val new_neig = new GraphState(l.head, g)
neighboursAcc(l.tail, List(new_neig) ++ acc, g)
}
}
neighboursAcc(g(loc), List(), g)
}
}
trait HillClimbing {
val max_iteration = 4
val start:State
def cost(state:State):Double
private def argmin(costs:List[Double]):Int = {
val best = costs.min
costs.indexOf(best)
}
private def next_best(states:List[State]):State = {
val costs = states map(x => cost(x))
val pos = argmin(costs)
states(pos)
}
def minimize():State = {
def minimizeAcc(iteration:Int, state:State):State =
{
if(iteration > max_iteration) state
else {
val neigs = state.neighbours
val next_state = next_best(neigs)
minimizeAcc(iteration+1, next_state)
}
}
minimizeAcc(0, start)
}
}
class GraphHillClimbing(start:GraphState, goal:GraphState) extends HillClimbing {
// ERROR 1 = start was State and now it is GraphState
// ERROR 2 = cost should take a State
def cost(current_state:GraphState):Double = {
val distance = goal.get_loc() - current_state.get_loc()
if(distance > 0 ) distance
else -distance
}
}
object RunHillClimbing {
def main(args: Array[String]) {
val G = Map[Int, List[Int]](1->List(2, 4, 5), 2->List(1, 3, 4), 3->List(2, 6), 4->List(1, 2, 5), 5->List(1, 4), 6->List(3))
val start = new GraphState(1, G)
val goal = new GraphState(6, G)
val hc = new GraphHillClimbing(start, goal)
print(hc.minimize())
}
}