mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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Added graph dfs challenge.
This commit is contained in:
Donne Martin
parent
bf0c1e927f
commit
43eb3f84fa
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@ -208,6 +208,7 @@ Challenges, solutions, and unit tests are presented in the form of **IPython/Jup
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| 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) |
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| 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) |
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| 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) |
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| 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) |
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| 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) |
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| 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) |
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| 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
graphs_trees/graph_dfs/__init__.py
Normal file
0
graphs_trees/graph_dfs/__init__.py
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209
graphs_trees/graph_dfs/dfs_challenge.ipynb
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209
graphs_trees/graph_dfs/dfs_challenge.ipynb
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@ -0,0 +1,209 @@
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"<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>"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Challenge Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Implement depth-first search on a graph.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)\n",
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"* [Solution Notebook](#Solution-Notebook)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Is the graph directed?\n",
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" * Yes\n",
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"* Can we assume we already have Graph and Node classes?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"Input:\n",
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"* `add_edge(source, destination, weight)`\n",
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"\n",
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"```\n",
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"graph.add_edge(0, 1, 5)\n",
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"graph.add_edge(0, 4, 3)\n",
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"graph.add_edge(0, 5, 2)\n",
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"graph.add_edge(1, 3, 5)\n",
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"graph.add_edge(1, 4, 4)\n",
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"graph.add_edge(2, 1, 6)\n",
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"graph.add_edge(3, 2, 7)\n",
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"graph.add_edge(3, 4, 8)\n",
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"```\n",
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"\n",
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"Result:\n",
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"* Order of nodes visited: [0, 1, 3, 2, 4, 5]"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"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."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run ../graph/graph.py\n",
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"%load ../graph/graph.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"def dfs(root, visit_func):\n",
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" # TODO: Implement me\n",
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" pass"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"**The following unit test is expected to fail until you solve the challenge.**"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run ../utils/results.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# %load test_dfs.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestDfs(object):\n",
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"\n",
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" def __init__(self):\n",
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" self.results = Results()\n",
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"\n",
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" def test_dfs(self):\n",
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" nodes = []\n",
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" graph = Graph()\n",
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" for id in range(0, 6):\n",
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" nodes.append(graph.add_node(id))\n",
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" graph.add_edge(0, 1, 5)\n",
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" graph.add_edge(0, 4, 3)\n",
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" graph.add_edge(0, 5, 2)\n",
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" graph.add_edge(1, 3, 5)\n",
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" graph.add_edge(1, 4, 4)\n",
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" graph.add_edge(2, 1, 6)\n",
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" graph.add_edge(3, 2, 7)\n",
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" graph.add_edge(3, 4, 8)\n",
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" dfs(nodes[0], self.results.add_result)\n",
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" assert_equal(str(self.results), \"[0, 1, 3, 2, 4, 5]\")\n",
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"\n",
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" print('Success: test_dfs')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestDfs()\n",
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" test.test_dfs()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution Notebook\n",
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"\n",
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"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."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 2",
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"language": "python",
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"name": "python2"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 2
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython2",
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"version": "2.7.10"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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231
graphs_trees/graph_dfs/dfs_solution.ipynb
Normal file
231
graphs_trees/graph_dfs/dfs_solution.ipynb
Normal file
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@ -0,0 +1,231 @@
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{
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||||
"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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||||
"source": [
|
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"<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>"
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||||
]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Solution Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Implement depth-first search on a graph.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Is the graph directed?\n",
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" * Yes\n",
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"* Can we assume we already have Graph and Node classes?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"Input:\n",
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"* `add_edge(source, destination, weight)`\n",
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"\n",
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"```\n",
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"graph.add_edge(0, 1, 5)\n",
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"graph.add_edge(0, 4, 3)\n",
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"graph.add_edge(0, 5, 2)\n",
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"graph.add_edge(1, 3, 5)\n",
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"graph.add_edge(1, 4, 4)\n",
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"graph.add_edge(2, 1, 6)\n",
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"graph.add_edge(3, 2, 7)\n",
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"graph.add_edge(3, 4, 8)\n",
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"```\n",
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"\n",
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"Result:\n",
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"* Order of nodes visited: [0, 1, 3, 2, 4, 5]"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"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",
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"\n",
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"* Visit the current node and mark it visited\n",
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"* Iterate through each adjacent node\n",
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" * If the node has not been visited, call dfs on it\n",
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"\n",
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"Complexity:\n",
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"* Time: O(V + E), where V = number of vertices and E = number of edges\n",
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"* Space: O(V + E)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run ../graph/graph.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"def dfs(root, visit_func):\n",
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" if root is None:\n",
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" return\n",
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" visit_func(root.id)\n",
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" root.visited = True\n",
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" for node in root.adjacent:\n",
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" if not node.visited:\n",
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" dfs(node, visit_func)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run ../utils/results.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting test_dfs.py\n"
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]
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}
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],
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"source": [
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"%%writefile test_dfs.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestDfs(object):\n",
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"\n",
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" def __init__(self):\n",
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" self.results = Results()\n",
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"\n",
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" def test_dfs(self):\n",
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" nodes = []\n",
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" graph = Graph()\n",
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" for id in range(0, 6):\n",
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" nodes.append(graph.add_node(id))\n",
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" graph.add_edge(0, 1, 5)\n",
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" graph.add_edge(0, 4, 3)\n",
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" graph.add_edge(0, 5, 2)\n",
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" graph.add_edge(1, 3, 5)\n",
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" graph.add_edge(1, 4, 4)\n",
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" graph.add_edge(2, 1, 6)\n",
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" graph.add_edge(3, 2, 7)\n",
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" graph.add_edge(3, 4, 8)\n",
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" dfs(nodes[0], self.results.add_result)\n",
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" assert_equal(str(self.results), \"[0, 1, 3, 2, 4, 5]\")\n",
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"\n",
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" print('Success: test_dfs')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestDfs()\n",
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" test.test_dfs()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Success: test_dfs\n"
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]
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}
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],
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"source": [
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"%run -i test_dfs.py"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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||||
"display_name": "Python 2",
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"language": "python",
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"name": "python2"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 2
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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||||
"nbconvert_exporter": "python",
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||||
"pygments_lexer": "ipython2",
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||||
"version": "2.7.10"
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||||
}
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||||
},
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||||
"nbformat": 4,
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"nbformat_minor": 0
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||||
}
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||||
34
graphs_trees/graph_dfs/test_dfs.py
Normal file
34
graphs_trees/graph_dfs/test_dfs.py
Normal file
|
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@ -0,0 +1,34 @@
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from nose.tools import assert_equal
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||||
|
||||
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()
|
||||
Loading…
Reference in New Issue
Block a user