scala.collection.immutable.RedBlack.scala Maven / Gradle / Ivy
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2005-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package immutable
/** A base class containing the implementations for `TreeMaps` and `TreeSets`.
*
* @since 2.3
*/
@serializable @SerialVersionUID(8691885935445612921L)
abstract class RedBlack[A] {
def isSmaller(x: A, y: A): Boolean
private def blacken[B](t: Tree[B]): Tree[B] = t match {
case RedTree(k, v, l, r) => BlackTree(k, v, l, r)
case t => t
}
private def mkTree[B](isBlack: Boolean, k: A, v: B, l: Tree[B], r: Tree[B]) =
if (isBlack) BlackTree(k, v, l, r) else RedTree(k, v, l, r)
@serializable
abstract class Tree[+B] {
def isEmpty: Boolean
def isBlack: Boolean
def lookup(x: A): Tree[B]
def update[B1 >: B](k: A, v: B1): Tree[B1] = blacken(upd(k, v))
def delete(k: A): Tree[B] = blacken(del(k))
def foreach[U](f: (A, B) => U)
@deprecated("use `foreach' instead")
def visit[T](input: T)(f: (T, A, B) => (Boolean, T)): (Boolean, T)
def toStream: Stream[(A,B)]
def iterator: Iterator[(A, B)]
@deprecated("use `iterator' instead") def elements = iterator
def upd[B1 >: B](k: A, v: B1): Tree[B1]
def del(k: A): Tree[B]
def smallest: NonEmpty[B]
def range(from: Option[A], until: Option[A]): Tree[B]
def first : A
def last : A
def count : Int
}
@serializable
abstract class NonEmpty[+B] extends Tree[B] {
def isEmpty = false
def key: A
def value: B
def left: Tree[B]
def right: Tree[B]
def lookup(k: A): Tree[B] =
if (isSmaller(k, key)) left.lookup(k)
else if (isSmaller(key, k)) right.lookup(k)
else this
def upd[B1 >: B](k: A, v: B1): Tree[B1] = {
def balanceLeft(isBlack: Boolean, z: A, zv: B, l: Tree[B1], d: Tree[B1]) = l match {
case RedTree(y, yv, RedTree(x, xv, a, b), c) =>
RedTree(y, yv, BlackTree(x, xv, a, b), BlackTree(z, zv, c, d))
case RedTree(x, xv, a, RedTree(y, yv, b, c)) =>
RedTree(y, yv, BlackTree(x, xv, a, b), BlackTree(z, zv, c, d))
case _ =>
mkTree(isBlack, z, zv, l, d)
}
def balanceRight(isBlack: Boolean, x: A, xv: B, a: Tree[B1], r: Tree[B1]) = r match {
case RedTree(z, zv, RedTree(y, yv, b, c), d) =>
RedTree(y, yv, BlackTree(x, xv, a, b), BlackTree(z, zv, c, d))
case RedTree(y, yv, b, RedTree(z, zv, c, d)) =>
RedTree(y, yv, BlackTree(x, xv, a, b), BlackTree(z, zv, c, d))
case _ =>
mkTree(isBlack, x, xv, a, r)
}
if (isSmaller(k, key)) balanceLeft(isBlack, key, value, left.upd(k, v), right)
else if (isSmaller(key, k)) balanceRight(isBlack, key, value, left, right.upd(k, v))
else mkTree(isBlack, k, v, left, right)
}
// Based on Stefan Kahrs' Haskell version of Okasaki's Red&Black Trees
// http://www.cse.unsw.edu.au/~dons/data/RedBlackTree.html
def del(k: A): Tree[B] = {
def balance(x: A, xv: B, tl: Tree[B], tr: Tree[B]) = (tl, tr) match {
case (RedTree(y, yv, a, b), RedTree(z, zv, c, d)) =>
RedTree(x, xv, BlackTree(y, yv, a, b), BlackTree(z, zv, c, d))
case (RedTree(y, yv, RedTree(z, zv, a, b), c), d) =>
RedTree(y, yv, BlackTree(z, zv, a, b), BlackTree(x, xv, c, d))
case (RedTree(y, yv, a, RedTree(z, zv, b, c)), d) =>
RedTree(z, zv, BlackTree(y, yv, a, b), BlackTree(x, xv, c, d))
case (a, RedTree(y, yv, b, RedTree(z, zv, c, d))) =>
RedTree(y, yv, BlackTree(x, xv, a, b), BlackTree(z, zv, c, d))
case (a, RedTree(y, yv, RedTree(z, zv, b, c), d)) =>
RedTree(z, zv, BlackTree(x, xv, a, b), BlackTree(y, yv, c, d))
case (a, b) =>
BlackTree(x, xv, a, b)
}
def subl(t: Tree[B]) = t match {
case BlackTree(x, xv, a, b) => RedTree(x, xv, a, b)
case _ => error("Defect: invariance violation; expected black, got "+t)
}
def balLeft(x: A, xv: B, tl: Tree[B], tr: Tree[B]) = (tl, tr) match {
case (RedTree(y, yv, a, b), c) =>
RedTree(x, xv, BlackTree(y, yv, a, b), c)
case (bl, BlackTree(y, yv, a, b)) =>
balance(x, xv, bl, RedTree(y, yv, a, b))
case (bl, RedTree(y, yv, BlackTree(z, zv, a, b), c)) =>
RedTree(z, zv, BlackTree(x, xv, bl, a), balance(y, yv, b, subl(c)))
case _ => error("Defect: invariance violation at "+right)
}
def balRight(x: A, xv: B, tl: Tree[B], tr: Tree[B]) = (tl, tr) match {
case (a, RedTree(y, yv, b, c)) =>
RedTree(x, xv, a, BlackTree(y, yv, b, c))
case (BlackTree(y, yv, a, b), bl) =>
balance(x, xv, RedTree(y, yv, a, b), bl)
case (RedTree(y, yv, a, BlackTree(z, zv, b, c)), bl) =>
RedTree(z, zv, balance(y, yv, subl(a), b), BlackTree(x, xv, c, bl))
case _ => error("Defect: invariance violation at "+left)
}
def delLeft = left match {
case _: BlackTree[_] => balLeft(key, value, left.del(k), right)
case _ => RedTree(key, value, left.del(k), right)
}
def delRight = right match {
case _: BlackTree[_] => balRight(key, value, left, right.del(k))
case _ => RedTree(key, value, left, right.del(k))
}
def append(tl: Tree[B], tr: Tree[B]): Tree[B] = (tl, tr) match {
case (Empty, t) => t
case (t, Empty) => t
case (RedTree(x, xv, a, b), RedTree(y, yv, c, d)) =>
append(b, c) match {
case RedTree(z, zv, bb, cc) => RedTree(z, zv, RedTree(x, xv, a, bb), RedTree(y, yv, cc, d))
case bc => RedTree(x, xv, a, RedTree(y, yv, bc, d))
}
case (BlackTree(x, xv, a, b), BlackTree(y, yv, c, d)) =>
append(b, c) match {
case RedTree(z, zv, bb, cc) => RedTree(z, zv, BlackTree(x, xv, a, bb), BlackTree(y, yv, cc, d))
case bc => balLeft(x, xv, a, BlackTree(y, yv, bc, d))
}
case (a, RedTree(x, xv, b, c)) => RedTree(x, xv, append(a, b), c)
case (RedTree(x, xv, a, b), c) => RedTree(x, xv, a, append(b, c))
}
// RedBlack is neither A : Ordering[A], nor A <% Ordered[A]
k match {
case _ if isSmaller(k, key) => delLeft
case _ if isSmaller(key, k) => delRight
case _ => append(left, right)
}
}
def smallest: NonEmpty[B] = if (left.isEmpty) this else left.smallest
def toStream: Stream[(A,B)] =
left.toStream ++ Stream((key,value)) ++ right.toStream
def iterator: Iterator[(A, B)] =
left.iterator ++ Iterator.single(Pair(key, value)) ++ right.iterator
def foreach[U](f: (A, B) => U) {
left foreach f
f(key, value)
right foreach f
}
@deprecated("use `foreach' instead")
def visit[T](input: T)(f: (T,A,B) => (Boolean, T)): (Boolean, T) = {
val left = this.left.visit(input)(f)
if (!left._1) return left
val middle = f(left._2, key, value)
if (!middle._1) return middle
return this.right.visit(middle._2)(f)
}
override def range(from: Option[A], until: Option[A]): Tree[B] = {
if (from == None && until == None) return this
if (from != None && isSmaller(key, from.get)) return right.range(from, until);
if (until != None && (isSmaller(until.get,key) || !isSmaller(key,until.get)))
return left.range(from, until);
val newLeft = left.range(from, None)
val newRight = right.range(None, until)
if ((newLeft eq left) && (newRight eq right)) this
else if (newLeft eq Empty) newRight.upd(key, value);
else if (newRight eq Empty) newLeft.upd(key, value);
else mkTree(isBlack, key, value, newLeft, newRight)
}
def first = if (left .isEmpty) key else left.first
def last = if (right.isEmpty) key else right.last
def count = 1 + left.count + right.count
}
@serializable
case object Empty extends Tree[Nothing] {
def isEmpty = true
def isBlack = true
def lookup(k: A): Tree[Nothing] = this
def upd[B](k: A, v: B): Tree[B] = RedTree(k, v, Empty, Empty)
def del(k: A): Tree[Nothing] = this
def smallest: NonEmpty[Nothing] = throw new NoSuchElementException("empty map")
def iterator: Iterator[(A, Nothing)] = Iterator.empty
def toStream: Stream[(A,Nothing)] = Stream.empty
def foreach[U](f: (A, Nothing) => U) {}
@deprecated("use `foreach' instead")
def visit[T](input: T)(f: (T, A, Nothing) => (Boolean, T)) = (true, input)
def range(from: Option[A], until: Option[A]) = this
def first = throw new NoSuchElementException("empty map")
def last = throw new NoSuchElementException("empty map")
def count = 0
}
@serializable
case class RedTree[+B](override val key: A,
override val value: B,
override val left: Tree[B],
override val right: Tree[B]) extends NonEmpty[B] {
def isBlack = false
}
@serializable
case class BlackTree[+B](override val key: A,
override val value: B,
override val left: Tree[B],
override val right: Tree[B]) extends NonEmpty[B] {
def isBlack = true
}
}
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