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 </pre><pre class="rust"><code><span class="doccomment">//! This module implements a simple binary tree.
 //!
 //! The tree supports inserting and retriving elements.
 //! Deleteing an element is not supported.
 //!
 //! [std::vec::Vec](https://doc.rust-lang.org/std/vec/struct.Vec.html) is used to implement the binary tree.

 </span><span class="attribute">#[cfg(all(feature = <span class="string">&quot;mesalock_sgx&quot;</span>, not(target_env = <span class="string">&quot;sgx&quot;</span>)))]
 </span><span class="kw">use </span>std::prelude::v1::<span class="kw-2">*</span>;

 <span class="kw">use </span>serde_derive::{Deserialize, Serialize};

 <span class="doccomment">/// Node of the binary tree.
 </span><span class="attribute">#[derive(Debug, Default, Serialize, Deserialize)]
 </span><span class="kw">pub struct </span>BinaryTreeNode&lt;T&gt; {
     <span class="doccomment">/// Store information in a node.
     </span><span class="kw">pub </span>value: T,

     <span class="doccomment">/// The index of the current node.
     </span>index: usize,

     <span class="doccomment">/// The index of the left child node. 0 means no left child.
     </span>left: usize, <span class="comment">// bigger than 0

     </span><span class="doccomment">/// The index of the right child node. 0 means of right child.
     </span>right: usize, <span class="comment">// bigger than 0
 </span>}

 <span class="kw">impl</span>&lt;T&gt; BinaryTreeNode&lt;T&gt; {
     <span class="doccomment">/// Generate a node with given value
     ///
     /// # Example
     /// ```
     /// use gbdt::binary_tree::BinaryTreeNode;
     /// let root = BinaryTreeNode::new(10);
     /// println!(&quot;{}&quot;, root.value);
     /// assert_eq!(10, root.value);
     /// ```
     </span><span class="kw">pub fn </span>new(value: T) -&gt; <span class="self">Self </span>{
         BinaryTreeNode {
             value,
             index: <span class="number">0</span>,
             left: <span class="number">0</span>,
             right: <span class="number">0</span>,
         }
     }
 }

 <span class="doccomment">/// The index to retrive the tree node. Always get the index value from [`BinaryTree`] APIs.
 /// Don&#39;t directly assign a value to an index.
 ///
 /// [`BinaryTree`]: struct.BinaryTree.html
 </span><span class="kw">pub type </span>TreeIndex = usize;

 <span class="doccomment">/// The binary tree.
 </span><span class="attribute">#[derive(Debug, Serialize, Deserialize)]
 </span><span class="kw">pub struct </span>BinaryTree&lt;T&gt; {
     tree: Vec&lt;BinaryTreeNode&lt;T&gt;&gt;,
 }

 <span class="kw">impl</span>&lt;T&gt; Default <span class="kw">for </span>BinaryTree&lt;T&gt; {
     <span class="kw">fn </span>default() -&gt; <span class="self">Self </span>{
         <span class="self">Self</span>::new()
     }
 }

 <span class="kw">impl</span>&lt;T&gt; BinaryTree&lt;T&gt; {
     <span class="doccomment">/// Build a new empty binary tree
     </span><span class="kw">pub fn </span>new() -&gt; <span class="self">Self </span>{
         BinaryTree { tree: Vec::new() }
     }

     <span class="doccomment">/// Returns true when the binary tree is empty
     </span><span class="kw">pub fn </span>is_empty(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
         <span class="self">self</span>.tree.is_empty()
     }

     <span class="doccomment">/// Add a node as the root node. Return the index of the root node.
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// let root_index = tree.add_root(root);
     /// assert_eq!(0, root_index);
     /// println!(&quot;{}&quot;, root_index)
     /// ```
     </span><span class="kw">pub fn </span>add_root(<span class="kw-2">&amp;mut </span><span class="self">self</span>, root: BinaryTreeNode&lt;T&gt;) -&gt; TreeIndex {
         <span class="self">self</span>.add_node(<span class="number">0</span>, <span class="bool-val">false</span>, root)
     }

     <span class="doccomment">/// Return the index of the root node.
     /// Call this API after inserting root node.
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// assert_eq!(0, tree.get_root_index());
     /// ```
     </span><span class="kw">pub fn </span>get_root_index(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; TreeIndex {
         <span class="number">0
     </span>}

     <span class="doccomment">/// Return the left child of the given `node`
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// let root_index = tree.add_root(root);
     /// let left_node = BinaryTreeNode::new(5.0);
     /// let _ = tree.add_left_node(root_index, left_node);
     /// let root = tree.get_node(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// let left_node = tree.get_left_child(root).expect(&quot;Didn&#39;t find left child&quot;);
     /// println!(&quot;{}&quot;, left_node.value);
     /// assert!((left_node.value - 5.0) &lt; 0.001)
     /// ```
     </span><span class="kw">pub fn </span>get_left_child(<span class="kw-2">&amp;</span><span class="self">self</span>, node: <span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;&gt; {
         <span class="kw">if </span>node.left == <span class="number">0 </span>{
             <span class="prelude-val">None
         </span>} <span class="kw">else </span>{
             <span class="self">self</span>.tree.get(node.left)
         }
     }

     <span class="doccomment">/// Return the right child of the given `node`
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// let root_index = tree.add_root(root);
     /// let right_node = BinaryTreeNode::new(5.0);
     /// let _ = tree.add_right_node(root_index, right_node);
     /// let root = tree.get_node(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// let right_node = tree.get_right_child(root).expect(&quot;Didn&#39;t find right child&quot;);
     /// println!(&quot;{}&quot;, right_node.value);
     ///assert!((right_node.value - 5.0) &lt; 0.001)
     /// ```
     </span><span class="kw">pub fn </span>get_right_child(<span class="kw-2">&amp;</span><span class="self">self</span>, node: <span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;&gt; {
         <span class="kw">if </span>node.right == <span class="number">0 </span>{
             <span class="prelude-val">None
         </span>} <span class="kw">else </span>{
             <span class="self">self</span>.tree.get(node.right)
         }
     }

     <span class="doccomment">/// Return the node with the given index
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;i32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10);
     /// let _ = tree.add_root(root);
     /// let root_index = tree.get_root_index();
     /// let root = tree.get_node(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// assert_eq!(10, root.value);
     /// ```
     </span><span class="kw">pub fn </span>get_node(<span class="kw-2">&amp;</span><span class="self">self</span>, index: TreeIndex) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;&gt; {
         <span class="self">self</span>.tree.get(index)
     }

     <span class="doccomment">/// Return the muttable reference of a node with the given index
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;i32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10);
     /// let _ = tree.add_root(root);
     /// let root_index = tree.get_root_index();
     /// let root = tree.get_node_mut(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// root.value = 11;
     /// assert_eq!(11, root.value);
     /// ```
     </span><span class="kw">pub fn </span>get_node_mut(<span class="kw-2">&amp;mut </span><span class="self">self</span>, index: TreeIndex) -&gt; <span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;mut </span>BinaryTreeNode&lt;T&gt;&gt; {
         <span class="self">self</span>.tree.get_mut(index)
     }

     <span class="doccomment">/// Add a node as the left child of a given `parent` node. Return the index of the added node.
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// let root_index = tree.add_root(root);
     /// let left_node = BinaryTreeNode::new(5.0);
     /// let _ = tree.add_left_node(root_index, left_node);
     /// let root = tree.get_node(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// let left_node = tree.get_left_child(root).expect(&quot;Didn&#39;t find left child&quot;);
     /// println!(&quot;{}&quot;, left_node.value);
     /// assert!((left_node.value - 5.0) &lt; 0.001)
     /// ```
     </span><span class="kw">pub fn </span>add_left_node(<span class="kw-2">&amp;mut </span><span class="self">self</span>, parent: TreeIndex, child: BinaryTreeNode&lt;T&gt;) -&gt; TreeIndex {
         <span class="self">self</span>.add_node(parent, <span class="bool-val">true</span>, child)
     }

     <span class="doccomment">/// Add a node as the right child of a given `parent` node. Return the index of the added node.
     /// # Example
     ///
     /// ``` rust
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     /// let root_index = tree.add_root(root);
     /// let right_node = BinaryTreeNode::new(5.0);
     /// let _ = tree.add_right_node(root_index, right_node);
     /// let root = tree.get_node(root_index).expect(&quot;Didn&#39;t find root node&quot;);
     /// let right_node = tree.get_right_child(root).expect(&quot;Didn&#39;t find right child&quot;);
     /// println!(&quot;{}&quot;, right_node.value);
     /// assert!((right_node.value - 5.0) &lt; 0.001)
     /// ```
     </span><span class="kw">pub fn </span>add_right_node(<span class="kw-2">&amp;mut </span><span class="self">self</span>, parent: TreeIndex, child: BinaryTreeNode&lt;T&gt;) -&gt; TreeIndex {
         <span class="self">self</span>.add_node(parent, <span class="bool-val">false</span>, child)
     }

     <span class="doccomment">/// The implmentation of adding a node to the tree. Return the index of the added node
     /// ``parent`` is the index of the parent node. For adding root node, `parent` can be arbitrary
     /// number. When the tree is empty, the node will be added as the root node.
     ///
     /// ``is_left`` means whether the node should be added as left child (true) or right child
     /// (false)
     ///
     /// ``child`` is the node to be added.
     </span><span class="kw">fn </span>add_node(
         <span class="kw-2">&amp;mut </span><span class="self">self</span>,
         parent: TreeIndex,
         is_left: bool,
         <span class="kw-2">mut </span>child: BinaryTreeNode&lt;T&gt;,
     ) -&gt; TreeIndex {
         child.index = <span class="self">self</span>.tree.len();
         <span class="self">self</span>.tree.push(child);
         <span class="kw">let </span>position = <span class="self">self</span>.tree.len() - <span class="number">1</span>;

         <span class="kw">if </span>position == <span class="number">0 </span>{
             <span class="kw">return </span>position;
         }
         <span class="kw">if let </span><span class="prelude-val">Some</span>(n) = <span class="self">self</span>.tree.get_mut(parent) {
             <span class="kw">if </span>is_left {
                 n.left = position;
             } <span class="kw">else </span>{
                 n.right = position;
             }
         };
         position
     }

     <span class="doccomment">/// For debug use. This API will print the whole tree.
     /// # Example
     /// ```
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     ///
     /// let root_index = tree.add_root(root);
     ///
     /// let n1 = BinaryTreeNode::new(5.0);
     /// let n2 = BinaryTreeNode::new(6.0);
     ///
     /// let n1_index = tree.add_left_node(root_index, n1);
     /// let n2_index = tree.add_right_node(root_index, n2);
     ///
     /// let n3 = BinaryTreeNode::new(7.0);
     /// let n4 = BinaryTreeNode::new(8.0);
     ///
     /// tree.add_left_node(n2_index, n3);
     /// tree.add_right_node(n2_index, n4);
     ///
     /// let n5 = BinaryTreeNode::new(9.0);
     ///
     /// tree.add_left_node(n1_index, n5);
     ///
     /// tree.print();
     ///
     /// // Output:
     /// //----10.0
     /// //    ----5.0
     /// //        ----9.0
     /// //    ----6.0
     /// //        ----7.0
     /// //        ----8.0
     ///  ```
     </span><span class="kw">pub fn </span>print(<span class="kw-2">&amp;</span><span class="self">self</span>)
     <span class="kw">where
         </span>T: std::fmt::Debug,
     {
         <span class="kw">let </span><span class="kw-2">mut </span>stack: Vec&lt;(usize, <span class="prelude-ty">Option</span>&lt;<span class="kw-2">&amp;</span>BinaryTreeNode&lt;T&gt;&gt;)&gt; = Vec::new();
         <span class="kw">let </span>root = <span class="self">self</span>.get_node(<span class="self">self</span>.get_root_index());
         stack.push((<span class="number">0</span>, root));
         <span class="kw">while </span>!stack.is_empty() {
             <span class="kw">let </span>next = stack.pop();
             <span class="kw">if let </span><span class="prelude-val">Some</span>((deep, node_opt)) = next {
                 <span class="kw">if let </span><span class="prelude-val">Some</span>(node) = node_opt {
                     <span class="kw">for </span>_i <span class="kw">in </span><span class="number">0</span>..deep {
                         <span class="macro">print!</span>(<span class="string">&quot;    &quot;</span>);
                     }
                     <span class="macro">println!</span>(<span class="string">&quot;----{:?}&quot;</span>, node.value);

                     stack.push((deep + <span class="number">1</span>, <span class="self">self</span>.get_right_child(node)));
                     stack.push((deep + <span class="number">1</span>, <span class="self">self</span>.get_left_child(node)));
                 }
             }
         }
     }

     <span class="doccomment">/// Get the amount of the nodes in this tree.
     /// # Example
     /// ```
     /// use gbdt::binary_tree::{BinaryTree, BinaryTreeNode};
     /// let mut tree: BinaryTree&lt;f32&gt; = BinaryTree::new();
     /// let root = BinaryTreeNode::new(10.0);
     ///
     /// let root_index = tree.add_root(root);
     ///
     /// let n1 = BinaryTreeNode::new(5.0);
     /// let n2 = BinaryTreeNode::new(6.0);
     ///
     /// let n1_index = tree.add_left_node(root_index, n1);
     /// let n2_index = tree.add_right_node(root_index, n2);
     ///
     /// assert_eq!(3, tree.len());
     </span><span class="kw">pub fn </span>len(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; usize {
         <span class="self">self</span>.tree.len()
     }
 }
 </code></pre></div>
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