{
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   "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": false
   },
   "outputs": [],
   "source": [
    "class Node(object):\n",
    "\n",
    "    def __init__(self, data):\n",
    "        self.data = data\n",
    "        self.left = None\n",
    "        self.right = None\n",
    "\n",
    "    def insert(self, data):\n",
    "        if data <= self.data:\n",
    "            if self.left is None:\n",
    "                self.left = type(self)(data)\n",
    "            else:\n",
    "                self.left.insert(data)\n",
    "        else:\n",
    "            if self.right is None:\n",
    "                self.right = type(self)(data)\n",
    "            else:\n",
    "                self.right.insert(data)\n",
    "\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": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%run ../utils/captured_output.py"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "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",
    "        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": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Success: test_dfs\n"
     ]
    }
   ],
   "source": [
    "%run -i test_dfs.py"
   ]
  }
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