get middle number

Author: email2liyang

scala/src/main/scala/ch29_heap_solutions/MiddleNumberKeeper.scala

@@ -0,0 +1,42 @@
+package ch29_heap_solutions
+
+import scala.collection.mutable
+
+class MiddleNumberKeeper(val percent: Double) {
+
+ def this() = this(0.5)
+
+ val bigTop = new mutable.PriorityQueue[Int]()
+ val smallTop = new mutable.PriorityQueue[Int]()(scala.math.Ordering.Int.reverse)
+
+
+ def put(num: Int): Unit = {
+ if (smallTop.nonEmpty && num >= smallTop.head) {
+ smallTop += num
+ adjustHeap()
+ return
+ }
+
+ //for any other scenario, we just put the item to bitTop then adjustHeap
+ bigTop += num
+ adjustHeap()
+ }
+
+ def get(): Option[Int] = {
+ bigTop.headOption
+ }
+
+ private[this] def adjustHeap(): Unit = {
+ val totalLength = smallTop.length + bigTop.length
+ //deal with bigTop
+ while (bigTop.length.doubleValue() / totalLength - percent > 0.0001) {
+ //move item from bigTop to smallTop
+ smallTop += bigTop.dequeue()
+ }
+
+ //deal with smallTop
+ while (smallTop.length.doubleValue() / totalLength - (1.0D - percent) > 0.0001) {
+ bigTop += smallTop.dequeue()
+ }
+ }
+}

scala/src/test/scala/ch29_heap_solutions/MiddleNumberKeeperTest.scala

@@ -0,0 +1,28 @@
+package ch29_heap_solutions
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class MiddleNumberKeeperTest extends FlatSpec with Matchers {
+
+ behavior of "MiddleNumberKeeperTest"
+
+ it should "get middle of the array" in {
+ val numKeeper = new MiddleNumberKeeper()
+ for (i <- Range(0, 10)) {
+ numKeeper.put(i)
+ }
+
+ numKeeper.get().get should equal(4)
+ }
+
+ it should "get 90% position of the array" in {
+ val numKeeper = new MiddleNumberKeeper(0.9)
+ for (i <- Range(0, 9)) {
+ numKeeper.put(i)
+ }
+ numKeeper.put(9)
+
+ numKeeper.get().get should equal(8)
+ }
+
+}