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   "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 a graph.\n",
    "\n",
    "* [Constraints](#Constraints)\n",
    "* [Test Cases](#Test-Cases)\n",
    "* [Algorithm](#Algorithm)\n",
    "* [Code](#Code)\n",
    "* [Unit Test](#Unit-Test)\n",
    "* [Solution Notebook](#Solution-Notebook)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Constraints\n",
    "\n",
    "* Is the graph directed?\n",
    "    * Yes\n",
    "* Do the edges have weights?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "Input:\n",
    "* `add_edge(source, destination, weight)`\n",
    "\n",
    "```\n",
    "graph.add_edge(0, 1, 5)\n",
    "graph.add_edge(0, 5, 2)\n",
    "graph.add_edge(1, 2, 3)\n",
    "graph.add_edge(2, 3, 4)\n",
    "graph.add_edge(3, 4, 5)\n",
    "graph.add_edge(3, 5, 6)\n",
    "graph.add_edge(4, 0, 7)\n",
    "graph.add_edge(5, 4, 8)\n",
    "graph.add_edge(5, 2, 9)\n",
    "```\n",
    "\n",
    "Result:\n",
    "* `source` and `destination` nodes within `graph` are connected with specified `weight`.\n",
    "\n",
    "Note: \n",
    "* We'll be using an OrderedDict to make the outputs more consistent and simplify our testing.\n",
    "* Graph will be used as a building block for more complex graph challenges."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "Refer to the [Solution Notebook](https://github.com/donnemartin/interactive-coding-challenges/graphs_trees/graphs/graph_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": false
   },
   "outputs": [],
   "source": [
    "from collections import OrderedDict\n",
    "\n",
    "\n",
    "class Node:\n",
    "\n",
    "    def __init__(self, id):\n",
    "        # TODO: Implement me\n",
    "        self.adjacent = OrderedDict()  # key = node, val = weight\n",
    "\n",
    "\n",
    "class Graph:\n",
    "\n",
    "    def __init__(self):\n",
    "        # TODO: Implement me\n",
    "        self.nodes = OrderedDict()  # key = node id, val = node\n",
    "\n",
    "    def add_node(self, id):\n",
    "        # TODO: Implement me\n",
    "        pass\n",
    "\n",
    "    def add_edge(self, source, dest, weight=0):\n",
    "        # TODO: Implement me\n",
    "        pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**The following unit test is expected to fail until you solve the challenge.**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# %load test_graph.py\n",
    "from nose.tools import assert_equal\n",
    "\n",
    "\n",
    "class TestGraph(object):\n",
    "\n",
    "    def test_graph(self):\n",
    "        graph = Graph()\n",
    "        for id in range(0, 6):\n",
    "            graph.add_node(id)\n",
    "        graph.add_edge(0, 1, 5)\n",
    "        graph.add_edge(0, 5, 2)\n",
    "        graph.add_edge(1, 2, 3)\n",
    "        graph.add_edge(2, 3, 4)\n",
    "        graph.add_edge(3, 4, 5)\n",
    "        graph.add_edge(3, 5, 6)\n",
    "        graph.add_edge(4, 0, 7)\n",
    "        graph.add_edge(5, 4, 8)\n",
    "        graph.add_edge(5, 2, 9)\n",
    "\n",
    "        assert_equal(graph.nodes[0].adjacent[graph.nodes[1]], 5)\n",
    "        assert_equal(graph.nodes[0].adjacent[graph.nodes[5]], 2)\n",
    "        assert_equal(graph.nodes[1].adjacent[graph.nodes[2]], 3)\n",
    "        assert_equal(graph.nodes[2].adjacent[graph.nodes[3]], 4)\n",
    "        assert_equal(graph.nodes[3].adjacent[graph.nodes[4]], 5)\n",
    "        assert_equal(graph.nodes[3].adjacent[graph.nodes[5]], 6)\n",
    "        assert_equal(graph.nodes[4].adjacent[graph.nodes[0]], 7)\n",
    "        assert_equal(graph.nodes[5].adjacent[graph.nodes[4]], 8)\n",
    "        assert_equal(graph.nodes[5].adjacent[graph.nodes[2]], 9)\n",
    "\n",
    "        print('Success: test_graph')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestGraph()\n",
    "    test.test_graph()\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/graphs/graph_solution.ipynb) for a discussion on algorithms and code solutions."
   ]
  }
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