BinaryTree+Traverse.swift

extension BinaryTree {
 
    func traverse() {
        print("\nPRE-ORDER TRAVERSE")
        self.preorder(self.rootNode)
        print("\n\nIN-ORDER TRAVERSE")
        self.inorder(self.rootNode)
        print("\n\nPOST-ORDER TRAVERSE")
        self.postorder(self.rootNode)
        print("\n")
    }
    
    // NOTE : LEFT IS ALWAYS LEFT OF RIGHT
    // NLR : NODE(i.e. Root/Parent Node) LEFT RIGHT
    
    // LNR : LEFT NODE RIGHT
    private func inorder(_ node: TreeNode<T>?) {
        guard let _ = node else { return }
        self.inorder(node?.leftNode)
        print("\(node!.data)", terminator: " ")
        self.inorder(node?.rightNode)
    }
    
    // NLR : NODE LEFT RIGHT
    private func preorder(_ node: TreeNode<T>?) {
        guard let _ = node else { return }
        print("\(node!.data)", terminator: " ")
        self.preorder(node?.leftNode)
        self.preorder(node?.rightNode)
    }
    
    // LRN :  LEFT RIGHT NODE
    private func postorder(_ node: TreeNode<T>?) {
        guard let _ = node else { return }
        self.postorder(node?.leftNode)
        self.postorder(node?.rightNode)
        print("\(node!.data)", terminator: " ")
    }
}