eu.shiftforward.apso.collection.Trie.scala Maven / Gradle / Ivy
package eu.shiftforward.apso.collection
/**
* An immutable implementation of a Trie (https://en.wikipedia.org/wiki/Trie).
*
* @param value the optional value of this node
* @param nodes the descendants of this node
*
* @tparam K the type param of keys in the nodes
* @tparam V the type param of values stored in the trie
*/
case class Trie[K, V](value: Option[V] = None, nodes: Map[K, Trie[K, V]] = Map[K, Trie[K, V]]()) {
/**
* Sets the provided value `v` for the key `k`.
*/
def set(k: Seq[K], v: V): Trie[K, V] = {
k match {
case Seq(h, t @ _*) =>
this.copy(value, nodes.get(h) match {
case Some(trie) =>
nodes.updated(h, trie.set(t, v))
case _ =>
nodes.updated(h, Trie[K, V]().set(t, v))
})
case _ =>
this.copy(Some(v), nodes)
}
}
/**
* Gets the value for the key `k`.
*/
def get(k: Seq[K]): Option[V] = {
k match {
case Seq(h, t @ _*) =>
nodes.get(h) match {
case Some(trie) => trie.get(t)
case _ => None
}
case _ =>
value
}
}
}