Heap.swift

class Heap {
  private var elements : [Int]
  
  init() {
    elements = [Int]()
  }
  
  func insert(number: Int) -> Void {
    if elements.count == 0 {
      elements.append(0)
      elements.append(number)
      return
    }
    
    elements.append(number)
    bubbleUpIfNeededFromIndex(elements.count - 1)
  }
  
  func minimum() -> Int {
    return elements.first! + 1
  }
  
  private func bubbleUpIfNeededFromIndex(index: Int) -> Void {
    if index <= 1 {return}
    let parentIndex = Int(index/2)
    if elements[index] < elements[parentIndex] {
      swapElements(atIndex: index, andIndex: parentIndex)
      bubbleUpIfNeededFromIndex(parentIndex)
    }
  }
  
  private func swapElements(atIndex firstIndex: Int, andIndex secondIndex: Int) -> Void {
    let firstValue = elements[firstIndex]
    let secondValue = elements[secondIndex]
    elements[secondIndex] = firstValue
    elements[firstIndex] = secondValue
  }
}