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Commit ac32f99

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Max binary heap and priority queue
1 parent 9639793 commit ac32f99

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6 files changed

+270
-1
lines changed

6 files changed

+270
-1
lines changed

‎src/main/kotlin/pl/dmichalski/algorithms/data_structures/_4_queue/Node.kt‎

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@@ -28,5 +28,4 @@ class Node(private var value: String) {
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return "Node(value='$value', next=$next)"
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}
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}
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package pl.dmichalski.algorithms.data_structures._7_max_binary_heap
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import java.lang.IllegalStateException
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class MaxBinaryHeap {
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private var values: MutableList<Int> = mutableListOf()
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fun insert(value: Int) {
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this.values.add(value)
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bubbleUp()
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}
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fun extractMax(): Int {
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if (values.size == 0) {
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throw IllegalStateException("Cannot extract max from an empty list")
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}
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val max = values[0]
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val end = values.removeLast()
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if(values.size > 1) {
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values[0] = end
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sinkDown()
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}
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return max
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}
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override fun toString(): String {
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return "Max binary heap values: $values\n"
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}
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private fun bubbleUp() {
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var idx = this.values.size - 1
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val element = this.values[idx]
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while (idx > 0) {
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val parentIdx = (idx - 1) / 2
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val parent = this.values[parentIdx]
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if (element > parent) {
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this.values[parentIdx] = element
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this.values[idx] = parent
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idx = parentIdx
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} else {
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break
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}
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}
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}
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private fun sinkDown() {
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var parentIndex = 0
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val parent = values[0]
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val length = values.size
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var leftChild: Int? = null
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var rightChild: Int?
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while(true) {
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var swapIdx: Int? = null
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val leftChildIdx = 2 * parentIndex + 1
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val rightChildIdx = 2 * parentIndex + 2
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if(leftChildIdx < length) {
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leftChild = values[leftChildIdx]
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if (leftChild > parent) {
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swapIdx = leftChildIdx
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}
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}
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if(rightChildIdx < length) {
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rightChild = values[rightChildIdx]
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if ((swapIdx == null && rightChild > parent) || (swapIdx != null && rightChild > leftChild!!)) {
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swapIdx = rightChildIdx
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}
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}
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if (swapIdx == null) {
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break
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}
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this.values[parentIndex] = this.values[swapIdx]
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this.values[swapIdx] = parent
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parentIndex = swapIdx
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}
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}
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}
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package pl.dmichalski.algorithms.data_structures._7_max_binary_heap
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object Runner {
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@JvmStatic
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fun main(args: Array<String>) {
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println("------------------ Initial max binary heap ------------------ ")
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var maxBinaryHeap = getMaxBinaryHeap()
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printMaxBinaryHeap(maxBinaryHeap)
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println("------------------ After extracting max value from max binary heap ------------------ ")
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maxBinaryHeap = getMaxBinaryHeap()
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val extractMax = maxBinaryHeap.extractMax()
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println("Removed element: $extractMax")
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printMaxBinaryHeap(maxBinaryHeap)
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}
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/**
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* It returns max binary heap like this:
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* <pre>
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* 55
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* / \
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* 18 45
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* / \ / \
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* 12 11 14 44
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*
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* </pre>
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*/
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private fun getMaxBinaryHeap(): MaxBinaryHeap {
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val maxBinaryHeap = MaxBinaryHeap()
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maxBinaryHeap.insert(12)
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maxBinaryHeap.insert(44)
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maxBinaryHeap.insert(14)
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maxBinaryHeap.insert(18)
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maxBinaryHeap.insert(11)
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maxBinaryHeap.insert(45)
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maxBinaryHeap.insert(58)
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return maxBinaryHeap
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}
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private fun printMaxBinaryHeap(maxBinaryHeap: MaxBinaryHeap) {
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println(maxBinaryHeap)
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}
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}
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package pl.dmichalski.algorithms.data_structures._8_priority_queue
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class Node(private var value: String, private var priority: Int) {
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fun getValue(): String {
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return value
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}
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fun getPriority(): Int {
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return priority
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}
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override fun toString(): String {
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return "Node(value='$value', priority=$priority)"
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}
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}
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package pl.dmichalski.algorithms.data_structures._8_priority_queue
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import java.lang.IllegalStateException
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class PriorityQueue {
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private var values: MutableList<Node> = mutableListOf()
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/**
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* O(log n) time complexity
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*/
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fun enqueue(value: String, priority: Int) {
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val node = Node(value, priority)
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this.values.add(node)
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bubbleUp()
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}
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/**
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* O(log n) time complexity
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*/
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fun dequeue(): Node {
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if (values.size == 0) {
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throw IllegalStateException("Cannot extract max from an empty list")
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}
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val min = values[0]
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val end = values.removeLast()
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if(values.size > 1) {
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values[0] = end
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sinkDown()
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}
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return min
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}
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override fun toString(): String {
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return "Priority queue values: $values\n"
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}
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private fun bubbleUp() {
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var idx = this.values.size - 1
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val element = this.values[idx]
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while (idx > 0) {
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val parentIdx = (idx - 1) / 2
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val parent = this.values[parentIdx]
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if (element.getPriority() >= parent.getPriority()) {
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break
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} else {
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this.values[parentIdx] = element
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this.values[idx] = parent
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idx = parentIdx
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}
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}
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}
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private fun sinkDown() {
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var parentIndex = 0
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val parent = values[0]
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val length = values.size
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var leftChild: Node? = null
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var rightChild: Node?
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while(true) {
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var swapIdx: Int? = null
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val leftChildIdx = 2 * parentIndex + 1
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val rightChildIdx = 2 * parentIndex + 2
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if(leftChildIdx < length) {
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leftChild = values[leftChildIdx]
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if (leftChild.getPriority() < parent.getPriority()) {
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swapIdx = leftChildIdx
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}
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}
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if(rightChildIdx < length) {
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rightChild = values[rightChildIdx]
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if ((swapIdx == null && rightChild.getPriority() < parent.getPriority()) || (swapIdx != null && rightChild.getPriority() < leftChild!!.getPriority())) {
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swapIdx = rightChildIdx
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}
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}
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if (swapIdx == null) {
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break
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}
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this.values[parentIndex] = this.values[swapIdx]
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this.values[swapIdx] = parent
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parentIndex = swapIdx
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}
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}
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}
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package pl.dmichalski.algorithms.data_structures._8_priority_queue
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object Runner {
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@JvmStatic
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fun main(args: Array<String>) {
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println("------------------ Initial priority queue ------------------ ")
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var priorityQueue = getPriorityQueue()
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printPriorityQueue(priorityQueue)
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println("------------------ Dequeue priority queue elements ------------------ ")
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priorityQueue = getPriorityQueue()
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val element = priorityQueue.dequeue()
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println("Dequeued element: $element")
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printPriorityQueue(priorityQueue)
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}
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private fun getPriorityQueue(): PriorityQueue {
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val priorityQueue = PriorityQueue()
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priorityQueue.enqueue("Medium priority", 5)
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priorityQueue.enqueue("Low priority", 10)
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priorityQueue.enqueue("Max priority", 1)
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priorityQueue.enqueue("Big priority", 3)
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return priorityQueue
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}
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private fun printPriorityQueue(maxBinaryHeap: PriorityQueue) {
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println(maxBinaryHeap)
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}
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}

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