BinaryTrees

Trees_BinaryTreeTraversals.swift

@@ -0,0 +1,103 @@
+import UIKit
+
+class BinaryNode<Element> {
+
+    var value: Element
+    var leftChild: BinaryNode?
+    var rightChild: BinaryNode?
+
+    init(_ value: Element) {
+        self.value = value
+    }
+}
+
+extension BinaryNode {
+
+    func inOrderTraversal(visit: (Element) -> Void) {         // leftChild -> Node -> RightChild
+        leftChild?.inOrderTraversal(visit: visit)
+        visit(value)
+        rightChild?.inOrderTraversal(visit: visit)
+    }
+
+    func postOrderTraversal(visit: (Element) -> Void) {       // leftChild -> RightChild -> Node
+        leftChild?.postOrderTraversal(visit: visit)
+        rightChild?.postOrderTraversal(visit: visit)
+        visit(value)
+    }
+
+    func preOrderTraversal(visit: (Element) -> Void) {        // Node -> leftChild -> rightChild
+        visit(value)
+        leftChild?.preOrderTraversal(visit: visit)
+        rightChild?.preOrderTraversal(visit: visit)
+    }
+}
+
+/*              10
+             /      \
+            9         2
+         /   \      /   \
+         1    3    4     6
+*/
+
+let ten = BinaryNode(10)
+let nine = BinaryNode(9)
+let two = BinaryNode(2)
+let one = BinaryNode(1)
+let three = BinaryNode(3)
+let four = BinaryNode(4)
+let six = BinaryNode(6)
+
+ten.leftChild = nine
+ten.rightChild = two
+
+nine.leftChild = one
+nine.rightChild = three
+
+two.leftChild = four
+two.rightChild = six
+
+print("\nIn Order Traversal")
+ten.inOrderTraversal {
+    print($0)             //1 9 3 10 4 2 6
+}
+
+print("\nPost Order Traversal")
+ten.postOrderTraversal {
+    print($0)             // 1 3 9 4 6 2 10
+}
+
+print("\nPre Order Traversal")
+ten.preOrderTraversal {
+    print($0)             //10 9 1 3 2 4 6
+}
+
+/*
+Outputs printed:
+
+    In Order Traversal
+    1
+    9
+    3
+    10
+    4
+    2
+    6
+
+    Post Order Traversal
+    1
+    3
+    9
+    4
+    6
+    2
+    10
+
+    Pre Order Traversal
+    10
+    9
+    1
+    3
+    2
+    4
+    6
+*/