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src/main/kotlin/it/norangeb/algorithms/exam/ThreeWayHeap.kt
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src/main/kotlin/it/norangeb/algorithms/exam/ThreeWayHeap.kt
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/*
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* MIT License
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*
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* Copyright (c) 2019 norangebit
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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package it.norangeb.algorithms.exam
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import arrow.core.None
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import arrow.core.Option
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import arrow.core.toOption
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class ThreeWayHeap<T> private constructor(
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private val shouldExchange: (T, T) -> Boolean
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) {
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private val array: Array<T?> = arrayOfNulls<Any>(1000) as Array<T?>
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private var size = 0
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fun insert(elem: T) {
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array[++size] = elem
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pushUp(size)
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}
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fun pop(): Option<T> {
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if (size <= 0)
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return None
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val elem = array[FIRST_ELEMENT]
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exchange(FIRST_ELEMENT, size)
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array[size--] = null
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pullDown(FIRST_ELEMENT)
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return elem.toOption()
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}
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fun peek(): Option<T> {
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if (size <= 0)
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return None
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return array[FIRST_ELEMENT].toOption()
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}
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private fun pushUp(k: Int) {
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val parent = k.parent()
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when {
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k <= FIRST_ELEMENT -> return
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shouldExchange(
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array[parent] ?: return,
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array[k] ?: return
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) -> {
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exchange(k, parent)
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pushUp(parent)
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}
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}
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}
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private fun pullDown(k: Int) {
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var i = k
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var child = child(i)
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while (child >= 0) {
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exchange(i, child)
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i = child
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child = child(i)
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}
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pushUp(i)
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}
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private fun child(k: Int): Int {
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val leftChild = array[k.leftChild()] ?: return -1
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val child = array[k.child()] ?: return k.leftChild()
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val rightChild = array[k.rightChild()] ?: return if (
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shouldExchange(leftChild, child)
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) k.child() else k.leftChild()
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return when {
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shouldExchange(leftChild, child) -> if (
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shouldExchange(child, rightChild)
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) k.rightChild() else k.child()
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else -> if (shouldExchange(leftChild, rightChild))
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k.rightChild() else k.leftChild()
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}
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}
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private fun exchange(i: Int, j: Int) {
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array[i] = array[j]
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.also { array[j] = array[i] }
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}
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companion object {
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fun <T : Comparable<T>> createMinHeap() = ThreeWayHeap<T> { t1, t2 ->
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t1 > t2
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}
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private fun Int.child() = this * THREE_WAY
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private fun Int.leftChild() = this * THREE_WAY - 1
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private fun Int.rightChild() = this * THREE_WAY + 1
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private fun Int.parent(): Int = (this + 1) / 3
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const val THREE_WAY = 3
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const val FIRST_ELEMENT = 1
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}
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}
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161
src/test/kotlin/it/norangeb/algorithms/exam/ThreeWayHeapTest.kt
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src/test/kotlin/it/norangeb/algorithms/exam/ThreeWayHeapTest.kt
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/*
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* MIT License
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*
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* Copyright (c) 2019 norangebit
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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package it.norangeb.algorithms.exam
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import arrow.core.None
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import arrow.core.Some
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import org.amshove.kluent.`should equal`
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import org.spekframework.spek2.Spek
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import org.spekframework.spek2.style.gherkin.Feature
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object ThreeWayHeapTest : Spek({
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Feature("three way heap") {
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Scenario("min heap") {
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val heap by memoized { ThreeWayHeap.createMinHeap<Int>() }
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When("add 23, 12, 45 into heap") {
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heap.insert(12)
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heap.insert(45)
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heap.insert(23)
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}
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Then("pop should equal 12") {
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heap.pop() `should equal` Some(12)
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}
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Then("peek should equal 23") {
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heap.peek() `should equal` Some(23)
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}
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When("add 25, 33, 24, 11, 15, 18, 34, 12 into heap") {
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heap.insert(25)
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heap.insert(18)
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heap.insert(11)
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heap.insert(33)
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heap.insert(24)
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heap.insert(12)
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heap.insert(15)
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heap.insert(34)
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}
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Then("pop should equal 11") {
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heap.pop() `should equal` Some(11)
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}
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Then("pop should equal 12") {
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heap.pop() `should equal` Some(12)
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}
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When("add 30, 10, 12, 5, 3, 8, 9, 2, 11") {
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heap.insert(12)
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heap.insert(8)
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heap.insert(3)
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heap.insert(30)
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heap.insert(2)
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heap.insert(10)
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heap.insert(5)
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heap.insert(11)
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heap.insert(9)
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}
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Then("pop should equal 2") {
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heap.pop() `should equal` Some(2)
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}
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Then("pop should equal 3") {
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heap.pop() `should equal` Some(3)
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}
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Then("pop should equal 5") {
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heap.pop() `should equal` Some(5)
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}
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Then("pop should equal 8") {
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heap.pop() `should equal` Some(8)
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}
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Then("pop should equal 9") {
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heap.pop() `should equal` Some(9)
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}
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Then("pop should equal 10") {
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heap.pop() `should equal` Some(10)
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}
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Then("pop should equal 11") {
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heap.pop() `should equal` Some(11)
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}
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Then("pop should equal 12") {
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heap.pop() `should equal` Some(12)
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}
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Then("pop should equal 15") {
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heap.pop() `should equal` Some(15)
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}
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Then("pop should equal 18") {
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heap.pop() `should equal` Some(18)
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}
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Then("pop should equal 23") {
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heap.pop() `should equal` Some(23)
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}
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Then("pop should equal 24") {
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heap.pop() `should equal` Some(24)
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}
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Then("pop should equal 25") {
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heap.pop() `should equal` Some(25)
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}
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Then("pop should equal 30") {
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heap.pop() `should equal` Some(30)
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}
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Then("pop should equal 33") {
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heap.pop() `should equal` Some(33)
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}
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Then("pop should equal 34") {
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heap.pop() `should equal` Some(34)
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}
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Then("pop should equal 45") {
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heap.pop() `should equal` Some(45)
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}
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Then("pop should equal None") {
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heap.pop() `should equal` None
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}
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Then("peek should equal None") {
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heap.peek() `should equal` None
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}
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}
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}
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})
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