Added graph dfs challenge.

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Donne Martin 2015-08-04 20:01:59 -04:00
parent bf0c1e927f
commit 43eb3f84fa
5 changed files with 475 additions and 0 deletions

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@ -208,6 +208,7 @@ Challenges, solutions, and unit tests are presented in the form of **IPython/Jup
| Implement breadth-first search on a tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_bfs/bfs_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_bfs/bfs_solution.ipynb) | | Implement breadth-first search on a tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_bfs/bfs_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_bfs/bfs_solution.ipynb) |
| Determine the height of a tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_height/height_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_height/height_solution.ipynb) | | Determine the height of a tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_height/height_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_height/height_solution.ipynb) |
| Implement a graph | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph/graph_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph/graph_solution.ipynb) | | Implement a graph | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph/graph_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph/graph_solution.ipynb) |
| Implement depth-first search on a graph | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_dfs/dfs_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_dfs/dfs_solution.ipynb) |
| Print a tree using pre-order traversal without recursion | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) | | Print a tree using pre-order traversal without recursion | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
| Determine the lowest common ancestor of two nodes | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) | | Determine the lowest common ancestor of two nodes | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |
| Transform a binary tree into a heap | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) | | Transform a binary tree into a heap | [Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md)│[Contribute](https://github.com/donnemartin/interactive-coding-challenges/blob/master/CONTRIBUTING.md) |

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@ -0,0 +1,209 @@
{
"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 search on 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",
"* Can we assume we already have Graph and Node classes?\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, 4, 3)\n",
"graph.add_edge(0, 5, 2)\n",
"graph.add_edge(1, 3, 5)\n",
"graph.add_edge(1, 4, 4)\n",
"graph.add_edge(2, 1, 6)\n",
"graph.add_edge(3, 2, 7)\n",
"graph.add_edge(3, 4, 8)\n",
"```\n",
"\n",
"Result:\n",
"* Order of nodes visited: [0, 1, 3, 2, 4, 5]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_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 ../graph/graph.py\n",
"%load ../graph/graph.py"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"def dfs(root, visit_func):\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": true
},
"outputs": [],
"source": [
"%run ../utils/results.py"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"# %load test_dfs.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestDfs(object):\n",
"\n",
" def __init__(self):\n",
" self.results = Results()\n",
"\n",
" def test_dfs(self):\n",
" nodes = []\n",
" graph = Graph()\n",
" for id in range(0, 6):\n",
" nodes.append(graph.add_node(id))\n",
" graph.add_edge(0, 1, 5)\n",
" graph.add_edge(0, 4, 3)\n",
" graph.add_edge(0, 5, 2)\n",
" graph.add_edge(1, 3, 5)\n",
" graph.add_edge(1, 4, 4)\n",
" graph.add_edge(2, 1, 6)\n",
" graph.add_edge(3, 2, 7)\n",
" graph.add_edge(3, 4, 8)\n",
" dfs(nodes[0], self.results.add_result)\n",
" assert_equal(str(self.results), \"[0, 1, 3, 2, 4, 5]\")\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](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_dfs/dfs_solution.ipynb) for a discussion on algorithms and code solutions."
]
}
],
"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
}

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@ -0,0 +1,231 @@
{
"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 search on a graph.\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",
"* Is the graph directed?\n",
" * Yes\n",
"* Can we assume we already have Graph and Node classes?\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, 4, 3)\n",
"graph.add_edge(0, 5, 2)\n",
"graph.add_edge(1, 3, 5)\n",
"graph.add_edge(1, 4, 4)\n",
"graph.add_edge(2, 1, 6)\n",
"graph.add_edge(3, 2, 7)\n",
"graph.add_edge(3, 4, 8)\n",
"```\n",
"\n",
"Result:\n",
"* Order of nodes visited: [0, 1, 3, 2, 4, 5]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"If we want to visit every node in a graph, we generally prefer depth-first search since it is simpler (no need to use a queue). For shortest path, we generally use breadth-first search.\n",
"\n",
"* Visit the current node and mark it visited\n",
"* Iterate through each adjacent node\n",
" * If the node has not been visited, call dfs on it\n",
"\n",
"Complexity:\n",
"* Time: O(V + E), where V = number of vertices and E = number of edges\n",
"* Space: O(V + E)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Code"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"%run ../graph/graph.py"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"def dfs(root, visit_func):\n",
" if root is None:\n",
" return\n",
" visit_func(root.id)\n",
" root.visited = True\n",
" for node in root.adjacent:\n",
" if not node.visited:\n",
" dfs(node, visit_func)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"%run ../utils/results.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 nose.tools import assert_equal\n",
"\n",
"\n",
"class TestDfs(object):\n",
"\n",
" def __init__(self):\n",
" self.results = Results()\n",
"\n",
" def test_dfs(self):\n",
" nodes = []\n",
" graph = Graph()\n",
" for id in range(0, 6):\n",
" nodes.append(graph.add_node(id))\n",
" graph.add_edge(0, 1, 5)\n",
" graph.add_edge(0, 4, 3)\n",
" graph.add_edge(0, 5, 2)\n",
" graph.add_edge(1, 3, 5)\n",
" graph.add_edge(1, 4, 4)\n",
" graph.add_edge(2, 1, 6)\n",
" graph.add_edge(3, 2, 7)\n",
" graph.add_edge(3, 4, 8)\n",
" dfs(nodes[0], self.results.add_result)\n",
" assert_equal(str(self.results), \"[0, 1, 3, 2, 4, 5]\")\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
}

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@ -0,0 +1,34 @@
from nose.tools import assert_equal
class TestDfs(object):
def __init__(self):
self.results = Results()
def test_dfs(self):
nodes = []
graph = Graph()
for id in range(0, 6):
nodes.append(graph.add_node(id))
graph.add_edge(0, 1, 5)
graph.add_edge(0, 4, 3)
graph.add_edge(0, 5, 2)
graph.add_edge(1, 3, 5)
graph.add_edge(1, 4, 4)
graph.add_edge(2, 1, 6)
graph.add_edge(3, 2, 7)
graph.add_edge(3, 4, 8)
dfs(nodes[0], self.results.add_result)
assert_equal(str(self.results), "[0, 1, 3, 2, 4, 5]")
print('Success: test_dfs')
def main():
test = TestDfs()
test.test_dfs()
if __name__ == '__main__':
main()