Add - AVL Tree, Binary Search Tree & Heap Sort.

sorts/HeapSort.swift

@@ -0,0 +1,19 @@
+extension Heap {
+  public mutating func sort() -> [T] {
+    for i in stride(from: (nodes.count - 1), through: 1, by: -1) {
+      nodes.swapAt(0, i)
+      shiftDown(from: 0, until: i)
+    }
+    return nodes
+  }
+}
+
+/*
+ Sorts an array using a heap.
+ Heapsort can be performed in-place, but it is not a stable sort.
+ */
+public func heapsort<T>(_ a: [T], _ sort: @escaping (T, T) -> Bool) -> [T] {
+  let reverseOrder = { i1, i2 in sort(i2, i1) }
+  var h = Heap(array: a, sort: reverseOrder)
+  return h.sort()
+}