kalub92

import Foundation

struct Stack {
    private var items: [String] = []
}

kalub92

import Foundation

struct MinHeap {
  var items: [Int] = []

  //Get Index
  private func getLeftChildIndex(_ parentIndex: Int) -> Int {
      return 2 * parentIndex + 1
  }
  private func getRightChildIndex(_ parentIndex: Int) -> Int {

kalub92

myHeap.peek() // Prints 2 to the console on the right in Swift Playgrounds
myHeap.poll()

dump(myHeap.items)

kalub92

var myHeap = MinHeap()

myHeap.add(2)
myHeap.add(10)
myHeap.add(8)
myHeap.add(9)
myHeap.add(7)
myHeap.add(3)
myHeap.add(4)

kalub92

mutating private func heapifyDown() {
  var index = 0
  while hasLeftChild(index) {
      var smallerChildIndex = getLeftChildIndex(index)
      if hasRightChild(index) && rightChild(index) < leftChild(index) {
          smallerChildIndex = getRightChildIndex(index)
      }

      if items[index] < items[smallerChildIndex] {
          break

kalub92

mutating private func heapifyUp() {
  var index = items.count - 1
  while hasParent(index) && parent(index) > items[index] {
      swap(indexOne: getParentIndex(index), indexTwo: index)
      index = getParentIndex(index)
  }
}

kalub92

mutating private func swap(indexOne: Int, indexTwo: Int) {
  let placeholder = items[indexOne]
  items[indexOne] = items[indexTwo]
  items[indexTwo] = placeholder
}

kalub92

mutating public func add(_ item: Int) {
  items.append(item)
  heapifyUp()
}

kalub92

mutating public func poll() -> Int {
  if items.count != 0 {
      let item = items[0]
      items[0] = items[items.count - 1]
      heapifyDown()
      items.removeLast()
      return item
  } else {
      fatalError()
  }

kalub92

public func peek() -> Int {
  if items.count != 0 {
      return items[0]
  } else {
      fatalError()
  }
}