A solution was missing (#35552)

My solution

curriculum/challenges/english/08-coding-interview-prep/data-structures/use-depth-first-search-in-a-binary-search-tree.english.md

@@ -116,6 +116,45 @@ BinarySearchTree.prototype = {
 <section id='solution'>
 
 ```js
-// solution required
+var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
+function Node(value) {
+    this.value = value;
+    this.left = null;
+    this.right = null;
+}
+function BinarySearchTree() {
+    this.root = null;
+    this.result = [];
+    
+    this.inorder = function(node) {        
+      if (!node) node = this.root;
+      if (!node) return null;
+
+      if (node.left) this.inorder(node.left);
+      this.result.push(node.value)
+      if (node.right) this.inorder(node.right);
+      return this.result;
+
+    };
+    this.preorder = function(node) {
+      if (!node) node = this.root;
+      if (!node) return null;
+      
+      this.result.push(node.value);
+      if (node.left) this.preorder(node.left);      
+      if (node.right) this.preorder(node.right);
+      return this.result;
+    };
+    this.postorder = function(node) {
+      if (!node) node = this.root;
+      if (!node) return null;
+
+      if (node.left) this.postorder(node.left);      
+      if (node.right) this.postorder(node.right);
+      this.result.push(node.value);
+      
+      return this.result;
+    };
+}
 ```
 </section>