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   "source": [
    "## Problem: Implement a linked list with insert, find, delete, and print methods.\n",
    "\n",
    "* [Clarifying Questions](#Clarifying-Questions)\n",
    "* [Test Cases](#Test-Cases)\n",
    "* [Algorithm](#Algorithm)\n",
    "* [Code](#Code)\n",
    "* [Pythonic-Code](#Pythonic-Code)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Clarifying Questions\n",
    "\n",
    "* Is this a singly or doubly linked list?\n",
    "    * Singly\n",
    "* Is this a circular list?\n",
    "    * No\n",
    "* Do we keep track of the tail or just the head?\n",
    "    * Just the head\n",
    "* Can you insert NULL values in the list?\n",
    "    * No"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "### Insert to Front\n",
    "\n",
    "* Insert a NULL\n",
    "* Insert in an empty list\n",
    "* Insert in a list with one element or more elements\n",
    "\n",
    "### Find\n",
    "\n",
    "* Coming soon\n",
    "\n",
    "### Delete\n",
    "\n",
    "* Coming soon\n",
    "\n",
    "### Print\n",
    "\n",
    "* Print an empty list\n",
    "* Print a list with one or more elements"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "### Insert to Front\n",
    "\n",
    "* If the data we are inserting is NULL, return\n",
    "* Create a node with the input data\n",
    "* If this is an empty list\n",
    "    * Assign the head to the node\n",
    "* Else\n",
    "    * Set the node.next to the head\n",
    "    * Set the head to the node\n",
    "\n",
    "Complexity:\n",
    "* Time: O(1)\n",
    "* Space: O(1), a new node is added\n",
    "\n",
    "### Find\n",
    "\n",
    "* Coming soon\n",
    "\n",
    "Complexity:\n",
    "* Time: O(n)\n",
    "* Space: In-place\n",
    "\n",
    "### Delete\n",
    "\n",
    "* Coming soon\n",
    "\n",
    "Complexity:\n",
    "* Time: O(n)\n",
    "* Space: In-place\n",
    "\n",
    "### Print\n",
    "\n",
    "* For each node\n",
    "    * Print the node's value\n",
    "    \n",
    "Complexity:\n",
    "* Time: O(n)\n",
    "* Space: In-place"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
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   "outputs": [],
   "source": [
    "class Node(object):\n",
    "    def __init__(self, data):\n",
    "        self.next = None\n",
    "        self.data = data\n",
    "        \n",
    "    def __str__(self):\n",
    "        return self.data\n",
    "\n",
    "class LinkedList(object):\n",
    "    def __init__(self, head):\n",
    "        self.head = head\n",
    "\n",
    "    def insert_to_front(self, data):\n",
    "        if data is None:\n",
    "            return\n",
    "        node = Node(data)\n",
    "        if self.head is None:\n",
    "            self.head = node\n",
    "        else:\n",
    "            node.next = self.head\n",
    "            self.head = node\n",
    "\n",
    "    def print_list(self):\n",
    "        curr_node = self.head\n",
    "        while curr_node is not None:\n",
    "            print(curr_node.data)\n",
    "            curr_node = curr_node.next"
   ]
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  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "10\n",
      "10\n",
      "bc\n",
      "a\n",
      "10\n"
     ]
    }
   ],
   "source": [
    "# Test insert_to_front\n",
    "# Insert in an empty list\n",
    "linked_list = LinkedList(None)\n",
    "linked_list.insert_to_front(10)\n",
    "linked_list.print_list()\n",
    "# Insert a NULL\n",
    "linked_list.insert_to_front(None)\n",
    "linked_list.print_list()\n",
    "# Insert in a list with one element or more elements\n",
    "linked_list.insert_to_front('a')\n",
    "linked_list.insert_to_front('bc')\n",
    "linked_list.print_list()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Test empty print\n",
    "linked_list = LinkedList(None)\n",
    "linked_list.print_list()"
   ]
  }
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