StarMirror/interactive-coding-challenges
1
0
Fork 0
mirror of https://github.com/donnemartin/interactive-coding-challenges.git synced 2024-03-22 13:11:13 +08:00
Code Issues Projects Releases Wiki Activity

Added bst validate challenge.

Browse Source
This commit is contained in:
Donne Martin 2015-08-14 19:30:09 -04:00
parent c595ea0fd7
commit f26f61e949
5 changed files with 457 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
README.md
View File

@ -208,6 +208,7 @@ Challenges, solutions, and unit tests are presented in the form of **IPython/Jup
| Create a binary search tree with minimal height from a sorted array | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_min/bst_min_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_min/bst_min_solution.ipynb) | | Create a binary search tree with minimal height from a sorted array | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_min/bst_min_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_min/bst_min_solution.ipynb) |
| Create a linked list for each level of a binary tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_level_lists/tree_level_lists_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_level_lists/tree_level_lists_solution.ipynb) | | Create a linked list for each level of a binary tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_level_lists/tree_level_lists_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_level_lists/tree_level_lists_solution.ipynb) |
| Check if a binary tree is balanced | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_solution.ipynb) | | Check if a binary tree is balanced | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_solution.ipynb) |
| Determine if a tree is a valid binary search tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_validate/bst_validate_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst_validate/bst_validate_solution.ipynb) |
| Implement a binary search tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst/bst_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst/bst_solution.ipynb) | | Implement a binary search tree | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst/bst_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/bst/bst_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) | | 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) |
| Implement breadth-first search on a graph | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_bfs/bfs_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_bfs/bfs_solution.ipynb) | | Implement breadth-first search on a graph | [Challenge](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_bfs/bfs_challenge.ipynb)│[Solution](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/graph_bfs/bfs_solution.ipynb) |

0
graphs_trees/bst_validate/__init__.py Normal file
View File

195
graphs_trees/bst_validate/bst_validate_challenge.ipynb Normal file
View File

@ -0,0 +1,195 @@
{
"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: Determine if a tree is a valid binary search tree.\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",
"* Can the tree have duplicates?\n",
" * Yes\n",
"* Can we assume we already have a Node class?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"<pre>\n",
"Valid:\n",
" 5\n",
" / \\\n",
" 5 8\n",
" / \\ /\n",
" 4 6 7\n",
"\n",
"Invalid:\n",
" 5\n",
" / \\\n",
" 5 8\n",
" / \\ /\n",
" 4 9 7\n",
"</pre>"
]
},
{
"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/bst_validate/bst_validate_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 ../bst/bst.py\n",
"%load ../bst/bst.py"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"def validate_bst(node):\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_bst_validate.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestBstValidate(object):\n",
"\n",
" def test_bst_validate(self):\n",
" node = Node(5)\n",
" insert(node, 8)\n",
" insert(node, 5)\n",
" insert(node, 6)\n",
" insert(node, 4)\n",
" insert(node, 7)\n",
" assert_equal(validate_bst(node), True)\n",
"\n",
" root = Node(5)\n",
" left = Node(5)\n",
" right = Node(8)\n",
" invalid = Node(20)\n",
" root.left = left\n",
" root.right = right\n",
" root.left.right = invalid\n",
" assert_equal(validate_bst(root), False)\n",
" print('Success: test_bst_validate')\n",
"\n",
"\n",
"def main():\n",
" test = TestBstValidate()\n",
" test.test_bst_validate()\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/bst_validate/bst_validate_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
}

228
graphs_trees/bst_validate/bst_validate_solution.ipynb Normal file
View File

@ -0,0 +1,228 @@
{
"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: Determine if a tree is a valid binary search 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 the tree have duplicates?\n",
" * Yes\n",
"* Can we assume we already have a Node class?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"<pre>\n",
"Valid:\n",
" 5\n",
" / \\\n",
" 5 8\n",
" / \\ /\n",
" 4 6 7\n",
"\n",
"Invalid:\n",
" 5\n",
" / \\\n",
" 5 8\n",
" \\ \n",
" 20\n",
"</pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"We'll use a recursive solution that valides left <= current < right, passing down the min and max values as we do a depth-first traversal.\n",
"\n",
"* If the node is None, return False\n",
"* If min is set and the node's value <= min, return False\n",
"* if max is set and the node's value > max, return False\n",
"* Recursively call the validate function on node.left, updating max\n",
"* Recursively call the validate function on node.right, updating min\n",
" \n",
"Complexity:\n",
"* Time: O(n)\n",
"* Space: O(h), where h is the height of the tree"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Code"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"%run ../bst/bst.py"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"def validate_bst(node):\n",
" return __validate_bst__(node, None, None)\n",
"\n",
"\n",
"def __validate_bst__(node, mininum, maximum):\n",
" if node is None:\n",
" return True\n",
" if mininum is not None and node.data <= mininum:\n",
" return False\n",
" if maximum is not None and node.data > maximum:\n",
" return False\n",
" if not __validate_bst__(node.left, mininum, node.data):\n",
" return False\n",
" if not __validate_bst__(node.right, node.data, maximum):\n",
" return False\n",
" return True"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Overwriting test_bst_validate.py\n"
]
}
],
"source": [
"%%writefile test_bst_validate.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestBstValidate(object):\n",
"\n",
" def test_bst_validate(self):\n",
" node = Node(5)\n",
" insert(node, 8)\n",
" insert(node, 5)\n",
" insert(node, 6)\n",
" insert(node, 4)\n",
" insert(node, 7)\n",
" assert_equal(validate_bst(node), True)\n",
"\n",
" root = Node(5)\n",
" left = Node(5)\n",
" right = Node(8)\n",
" invalid = Node(20)\n",
" root.left = left\n",
" root.right = right\n",
" root.left.right = invalid\n",
" assert_equal(validate_bst(root), False)\n",
"\n",
" print('Success: test_bst_validate')\n",
"\n",
"\n",
"def main():\n",
" test = TestBstValidate()\n",
" test.test_bst_validate()\n",
"\n",
"\n",
"if __name__ == '__main__':\n",
" main()"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Success: test_bst_validate\n"
]
}
],
"source": [
"%run -i test_bst_validate.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
}

33
graphs_trees/bst_validate/test_bst_validate.py Normal file
View File

@ -0,0 +1,33 @@
from nose.tools import assert_equal
class TestBstValidate(object):
def test_bst_validate(self):
node = Node(5)
insert(node, 8)
insert(node, 5)
insert(node, 6)
insert(node, 4)
insert(node, 7)
assert_equal(validate_bst(node), True)
root = Node(5)
left = Node(5)
right = Node(8)
invalid = Node(20)
root.left = left
root.right = right
root.left.right = invalid
assert_equal(validate_bst(root), False)
print('Success: test_bst_validate')
def main():
test = TestBstValidate()
test.test_bst_validate()
if __name__ == '__main__':
main()