Merge pull request TheAlgorithms#16 from gustavotiecker/feature/tree

add basic tree implementation

trees/tree.swift

@@ -0,0 +1,58 @@
+import Foundation
+
+public class TreeNode<T> {
+    public var value: T
+
+    public weak var parent: TreeNode?
+    public var children = [TreeNode<T>]()
+
+    public init(value: T) {
+        self.value = value
+    }
+
+    public func addChild(_ node: TreeNode<T>) {
+        children.append(node)
+        node.parent = self
+    }
+}
+
+/* Checks the node's value property, if there is no match, check the child nodes.
+Repeat the same process recursively */
+extension TreeNode where T: Equatable {
+    func search(_ value: T) -> TreeNode? {
+        if value == self.value {
+            return self
+        }
+        for child in children {
+            if let found = child.search(value) {
+                return found
+            }
+        }
+        return nil
+    }
+}
+
+// The code below can be used for testing
+let tree = TreeNode<String>(value: "animals")
+
+let reptilesNode = TreeNode<String>(value: "reptiles")
+let mammalsNode = TreeNode<String>(value: "mammals")
+
+let lizardsNode = TreeNode<String>(value: "lizards")
+let snakesNode = TreeNode<String>(value: "snakes")
+
+let dogsNode = TreeNode<String>(value: "dogs")
+let humansNode = TreeNode<String>(value: "humans")
+
+tree.addChild(reptilesNode)
+tree.addChild(mammalsNode)
+
+reptilesNode.addChild(lizardsNode)
+reptilesNode.addChild(snakesNode)
+
+mammalsNode.addChild(dogsNode)
+mammalsNode.addChild(humansNode)
+
+print(tree.search("humans")?.value)
+print(tree.search("lizards")?.value)
+print(tree.search("dragons")?.value)