diff --git a/graphs_trees/tree_dfs/__init__.py b/graphs_trees/tree_dfs/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/graphs_trees/tree_dfs/dfs_challenge.ipynb b/graphs_trees/tree_dfs/dfs_challenge.ipynb
new file mode 100644
index 0000000..5c12580
--- /dev/null
+++ b/graphs_trees/tree_dfs/dfs_challenge.ipynb
@@ -0,0 +1,234 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<small><i>This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).</i></small>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Challenge Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Implement depth-first searches (in-order, pre-order, post-order traversals) on a binary tree.\n",
+    "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "* Can we assume we already have a Node class with an insert method?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "### In-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
+    "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
+    "\n",
+    "### Pre-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 5, 2, 1, 3, 8\n",
+    "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
+    "\n",
+    "### Post-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 1, 3, 2, 8, 5\n",
+    "* 1, 2, 3, 4, 5 -> 5, 4, 3, 2, 1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [solution notebook](https://github.com/donnemartin/interactive-coding-challenges/graphs_trees/tree_dfs/dfs_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "%run ../bst/bst.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "class MyNode(Node):\n",
+    "    def in_order_traversal(self, visit_func):\n",
+    "        # TODO: Implement me\n",
+    "\n",
+    "    def pre_order_traversal(self, visit_func):\n",
+    "        # TODO: Implement me\n",
+    "\n",
+    "    def post_order_traversal(self, visit_func):\n",
+    "        # TODO: Implement me"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "%run ../utils/captured_output.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "# %load test_dfs.py\n",
+    "from __future__ import print_function\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestDfs(object):\n",
+    "\n",
+    "    def test_dfs(self):\n",
+    "        root = Node(5)\n",
+    "        root.insert(2)\n",
+    "        root.insert(8)\n",
+    "        root.insert(1)\n",
+    "        root.insert(3)\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.in_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12358')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.pre_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '52138')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.post_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '13285')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.bfs(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '52813')\n",
+    "\n",
+    "        root = Node(1)\n",
+    "        root.insert(2)\n",
+    "        root.insert(3)\n",
+    "        root.insert(4)\n",
+    "        root.insert(5)\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.in_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12345')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.pre_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12345')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.post_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '54321')\n",
+    "\n",
+    "        print('Success: test_dfs')\n",
+    "\n",
+    "\n",
+    "def main():\n",
+    "    test = TestDfs()\n",
+    "    test.test_dfs()\n",
+    "\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Solution Notebook\n",
+    "\n",
+    "Review the [solution notebook](https://github.com/donnemartin/interactive-coding-challenges/graphs_trees/tree_dfs/dfs_solution.ipynb) for a discussion on algorithms and code solutions."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.10"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/graphs_trees/tree_dfs/dfs_solution.ipynb b/graphs_trees/tree_dfs/dfs_solution.ipynb
new file mode 100644
index 0000000..0a0b26d
--- /dev/null
+++ b/graphs_trees/tree_dfs/dfs_solution.ipynb
@@ -0,0 +1,294 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<small><i>This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).</i></small>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Solution Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Implement depth-first searches (in-order, pre-order, post-order traversals) on a binary tree.\n",
+    "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "* Can we assume we already have a Node class with an insert method?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "### In-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
+    "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
+    "\n",
+    "### Pre-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 5, 2, 1, 3, 8\n",
+    "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
+    "\n",
+    "### Post-Order Traversal\n",
+    "\n",
+    "* 5, 2, 8, 1, 3 -> 1, 3, 2, 8, 5\n",
+    "* 1, 2, 3, 4, 5 -> 5, 4, 3, 2, 1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "## Test Cases\n",
+    "\n",
+    "### In-Order Traversal\n",
+    "\n",
+    "* Recursively call in-order traversal on the left child\n",
+    "* Visit the current node\n",
+    "* Recursively call in-order traversal on the right child\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n)\n",
+    "* Space: O(log n)\n",
+    "\n",
+    "Note:\n",
+    "* This is a form of a depth-first traversal\n",
+    "\n",
+    "### Pre-Order Traversal\n",
+    "\n",
+    "* Visit the current node\n",
+    "* Recursively call pre-order traversal on the left child\n",
+    "* Recursively call pre-order traversal on the right child\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n)\n",
+    "* Space: O(log n)\n",
+    "\n",
+    "Note:\n",
+    "* This is a form of a depth-first traversal\n",
+    "\n",
+    "### Post-Order Traversal\n",
+    "\n",
+    "* Recursively call post-order traversal on the left child\n",
+    "* Recursively call post-order traversal on the right child\n",
+    "* Visit the current node\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n)\n",
+    "* Space: O(log n)\n",
+    "\n",
+    "Note:\n",
+    "* This is a form of a depth-first traversal"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "%run ../bst/bst.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "class MyNode(Node):\n",
+    "    def in_order_traversal(self, visit_func):\n",
+    "        if self.left is not None:\n",
+    "            self.left.in_order_traversal(visit_func)\n",
+    "        visit_func(self.data)\n",
+    "        if self.right is not None:\n",
+    "            self.right.in_order_traversal(visit_func)\n",
+    "\n",
+    "    def pre_order_traversal(self, visit_func):\n",
+    "        visit_func(self.data)\n",
+    "        if self.left is not None:\n",
+    "            self.left.pre_order_traversal(visit_func)\n",
+    "        if self.right is not None:\n",
+    "            self.right.pre_order_traversal(visit_func)\n",
+    "\n",
+    "    def post_order_traversal(self, visit_func):\n",
+    "        if self.left is not None:\n",
+    "            self.left.post_order_traversal(visit_func)\n",
+    "        if self.right is not None:\n",
+    "            self.right.post_order_traversal(visit_func)\n",
+    "        visit_func(self.data)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "%run ../utils/captured_output.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Overwriting test_dfs.py\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%writefile test_dfs.py\n",
+    "from __future__ import print_function\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestDfs(object):\n",
+    "\n",
+    "    def test_dfs(self):\n",
+    "        root = Node(5)\n",
+    "        root.insert(2)\n",
+    "        root.insert(8)\n",
+    "        root.insert(1)\n",
+    "        root.insert(3)\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.in_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12358')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.pre_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '52138')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.post_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '13285')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.bfs(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '52813')\n",
+    "\n",
+    "        root = Node(1)\n",
+    "        root.insert(2)\n",
+    "        root.insert(3)\n",
+    "        root.insert(4)\n",
+    "        root.insert(5)\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.in_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12345')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.pre_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '12345')\n",
+    "\n",
+    "        with captured_output() as (out, err):\n",
+    "            root.post_order_traversal(sys.stdout.write)\n",
+    "            assert_equal(out.getvalue().strip(), '54321')\n",
+    "\n",
+    "        print('Success: test_dfs')\n",
+    "\n",
+    "\n",
+    "def main():\n",
+    "    test = TestDfs()\n",
+    "    test.test_dfs()\n",
+    "\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Success: test_dfs\n"
+     ]
+    }
+   ],
+   "source": [
+    "%run -i test_dfs.py"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.10"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/graphs_trees/tree_dfs/test_dfs.py b/graphs_trees/tree_dfs/test_dfs.py
new file mode 100644
index 0000000..f5763e5
--- /dev/null
+++ b/graphs_trees/tree_dfs/test_dfs.py
@@ -0,0 +1,57 @@
+from __future__ import print_function
+from nose.tools import assert_equal
+
+
+class TestDfs(object):
+
+    def test_dfs(self):
+        root = Node(5)
+        root.insert(2)
+        root.insert(8)
+        root.insert(1)
+        root.insert(3)
+
+        with captured_output() as (out, err):
+            root.in_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12358')
+
+        with captured_output() as (out, err):
+            root.pre_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '52138')
+
+        with captured_output() as (out, err):
+            root.post_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '13285')
+
+        with captured_output() as (out, err):
+            root.bfs(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '52813')
+
+        root = Node(1)
+        root.insert(2)
+        root.insert(3)
+        root.insert(4)
+        root.insert(5)
+
+        with captured_output() as (out, err):
+            root.in_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12345')
+
+        with captured_output() as (out, err):
+            root.pre_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12345')
+
+        with captured_output() as (out, err):
+            root.post_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '54321')
+
+        print('Success: test_dfs')
+
+
+def main():
+    test = TestDfs()
+    test.test_dfs()
+
+
+if __name__ == '__main__':
+    main()
\ No newline at end of file