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codility solution
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import scala.collection.immutable.HashMap | |
object Demo extends App { | |
sealed trait Input | |
object Input{ | |
final case class IncrementCounter(humanIndex: Int) extends Input | |
case object MaxCounter extends Input | |
def fromInt(n: Int, arraySize: Int): Input = if (n <= arraySize){ | |
IncrementCounter(n) | |
} else { | |
MaxCounter | |
} | |
} | |
final case class State(mapping: Map[State.ArrayIndex, Int], max: Int, min: Int) { | |
def get(arrayIndex: State.ArrayIndex): Int = mapping.get(arrayIndex).filter(_ > min).getOrElse(min) | |
def incrementByOne(arrayIndex: State.ArrayIndex): State = { | |
val newValue = get(arrayIndex) + 1 | |
val newMax = if(newValue > max){newValue} else max | |
copy(mapping = mapping.updated(arrayIndex, newValue), max = newMax) | |
} | |
def setAllToMax: State = copy(min = max) | |
} | |
object State{ | |
final case class ArrayIndex(value: Int) extends AnyVal | |
object ArrayIndex{ | |
def fromHumanIndex(i: Int): ArrayIndex = ArrayIndex(i - 1) | |
} | |
def empty: State = State(HashMap.empty, max = 0, min = 0) | |
} | |
def solution(n: Int, a: Array[Int]): Array[Int] = { | |
val state = a.toList.foldLeft(State.empty){ case (s, i) => | |
Input.fromInt(i, n) match { | |
case Input.IncrementCounter(humanIndex) => s.incrementByOne(State.ArrayIndex.fromHumanIndex(humanIndex)) | |
case Input.MaxCounter => s.setAllToMax | |
} | |
} | |
val response = new Array[Int](n) | |
Range(0, n).foreach( i => | |
response(i) = state.get(State.ArrayIndex(i)) | |
) | |
response | |
} | |
println( | |
solution( | |
5, | |
Array(3, 4, 4, 6, 1, 4, 4) | |
).mkString("Array(", ", ", ")") | |
) | |
} |
The second revision which uses a fold (as opposed to the foreach
based first revision that uses Unit
return type for State methods, would not pass 100% on performance score unless you add the a.toList
bit. not exactly sure why.
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The idea behind this solution is:
n=5, a= Array(1,1,1,1,1,1,1,1,...)
min
,max
cache the global information about our mappings and save us the dynamic lookup.setAllToMax
/max_counter
doesn't go around and update all the existing values.Array.fill
ing withmin
at the end. Think about the parameters:n=5, a= Array(1,6,6,6,6,6,6,6,6,...)