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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "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)."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Solution Notebook"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Problem: Implement breadth-first traversal 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\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes\n",
    "* What should we do with each node when we process it?\n",
    "    * Call an input method `visit_func` on the node"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "### Breadth-First Traversal\n",
    "* 5, 2, 8, 1, 3 -> 5, 2, 8, 1, 3"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "* Initialize queue with root\n",
    "* While queue is not empty\n",
    "    * Dequeue and print the node\n",
    "    * Queue the left child\n",
    "    * Queue the right child\n",
    "\n",
    "Complexity:\n",
    "* Time: O(n)\n",
    "* Space: O(n), extra space for the queue"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "%run ../bst/bst.py"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "from collections import deque\n",
    "\n",
    "\n",
    "class BstBfs(Bst):\n",
    "\n",
    "    def bfs(self, visit_func):\n",
    "        if self.root is None:\n",
    "            raise TypeError('root is None')\n",
    "        queue = deque()\n",
    "        queue.append(self.root)\n",
    "        while queue:\n",
    "            node = queue.popleft()\n",
    "            visit_func(node)\n",
    "            if node.left is not None:\n",
    "                queue.append(node.left)\n",
    "            if node.right is not None:\n",
    "                queue.append(node.right)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "%run ../utils/results.py"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Overwriting test_bfs.py\n"
     ]
    }
   ],
   "source": [
    "%%writefile test_bfs.py\n",
    "import unittest\n",
    "\n",
    "\n",
    "class TestBfs(unittest.TestCase):\n",
    "\n",
    "    def __init__(self, *args, **kwargs):\n",
    "        super(TestBfs, self).__init__()\n",
    "        self.results = Results()\n",
    "\n",
    "    def test_bfs(self):\n",
    "        bst = BstBfs(Node(5))\n",
    "        bst.insert(2)\n",
    "        bst.insert(8)\n",
    "        bst.insert(1)\n",
    "        bst.insert(3)\n",
    "        bst.bfs(self.results.add_result)\n",
    "        self.assertEqual(str(self.results), '[5, 2, 8, 1, 3]')\n",
    "\n",
    "        print('Success: test_bfs')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestBfs()\n",
    "    test.test_bfs()\n",
    "\n",
    "\n",
    "if __name__ == '__main__':\n",
    "    main()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Success: test_bfs\n"
     ]
    }
   ],
   "source": [
    "%run -i test_bfs.py"
   ]
  }
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