Exercise: Binary Tree

A binary tree is a tree-type data structure where every node has two children (left and right). We will create a tree where each node stores a value. For a given node N, all nodes in a N's left subtree contain smaller values, and all nodes in N's right subtree will contain larger values. A given value should only be stored in the tree once, i.e. no duplicate nodes.

Implement the following types, so that the given tests pass.

# // Copyright 2023 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
{{#include exercise.rs:types}}

// Implement `new` for `Node`.
// Implement `new`, `insert`, `len`, and `has` for `Subtree`.

{{#include exercise.rs:tests}}