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Added queue challenge.

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Donne Martin
2015-07-02 23:05:10 -04:00
parent 861d7bd25b
commit 1d9e3ad495
5 changed files with 305 additions and 20 deletions
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0
stacks_queues/queue_list/__init__.py Normal file
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6
stacks_queues/queue_list/queue_list.py
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@@ -1,12 +1,11 @@
# Need to avoid naming this queue.py as it
# will conflict with IPython Notebook
class Node(object): class Node(object):
def __init__(self, data): def __init__(self, data):
self.data = data self.data = data
self.next = None self.next = None
class Queue(object): class Queue(object):
def __init__(self): def __init__(self):
self.first = None self.first = None
self.last = None self.last = None
@@ -24,6 +23,7 @@ class Queue(object):
# Empty list # Empty list
if self.first is None and self.last is None: if self.first is None and self.last is None:
return None return None
# Remove only element from a one element list # Remove only element from a one element list
elif self.first == self.last: elif self.first == self.last:
data = self.first.data data = self.first.data

217
stacks_queues/queue_list/queue_list_challenge.ipynb Normal file
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@@ -0,0 +1,217 @@
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges).</i></small>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Challenge Notebook"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Problem: Implement a queue with enqueue and dequeue methods using a linked list.\n",
"\n",
"* [Constraints](#Constraints)\n",
"* [Test Cases](#Test-Cases)\n",
"* [Algorithm](#Algorithm)\n",
"* [Code](#Code)\n",
"* [Unit Test](#Unit-Test)\n",
"* [Pythonic-Code](#Pythonic-Code)\n",
"* [Solution Notebook](#Solution-Notebook)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Constraints\n",
"\n",
"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
"\n",
"* If there is one item in the list, do you expect the first and last pointers to both point to it?\n",
" * Yes\n",
"* If there are no items on the list, do you expect the first and last pointers to be NULL?\n",
" * Yes\n",
"* If you dequeue on an empty queue, does that return None?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"### Enqueue\n",
"\n",
"* Enqueue to an empty queue\n",
"* Enqueue to a non-empty queue\n",
"\n",
"### Dequeue\n",
"\n",
"* Dequeue an empty queue -> None\n",
"* Dequeue a queue with one element\n",
"* Dequeue a queue with more than one element"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/stacks_queues/queue_list/queue_list_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": [
"class Node(object):\n",
" \n",
" def __init__(self, data):\n",
" self.data = data\n",
" self.next = None\n",
"\n",
"class Queue(object):\n",
" \n",
" def __init__(self):\n",
" self.first = None\n",
" self.last = None\n",
"\n",
" def enqueue(self, data):\n",
" node = Node(data)\n",
" if self.first is None and self.last is None:\n",
" self.first = node\n",
" self.last = node\n",
" else:\n",
" self.last.next = node\n",
" self.last = node\n",
"\n",
" def dequeue(self):\n",
" # Empty list\n",
" if self.first is None and self.last is None:\n",
" return None\n",
" \n",
" # Remove only element from a one element list\n",
" elif self.first == self.last:\n",
" data = self.first.data\n",
" self.first = None\n",
" self.last = None\n",
" return data\n",
" else:\n",
" data = self.first.data\n",
" self.first = self.first.next\n",
" return data"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test\n",
"\n",
"\n",
"\n",
"**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_queue_list.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestQueue(object):\n",
" \n",
" # TODO: It would be better if we had unit tests for each\n",
" # method in addition to the following end-to-end test\n",
" def test_end_to_end(self):\n",
" print('Test: Dequeue an empty queue')\n",
" queue = Queue()\n",
" assert_equal(queue.dequeue(), None)\n",
"\n",
" print('Test: Enqueue to an empty queue')\n",
" queue.enqueue(1)\n",
"\n",
" print('Test: Dequeue a queue with one element')\n",
" assert_equal(queue.dequeue(), 1)\n",
"\n",
" print('Test: Enqueue to a non-empty queue')\n",
" queue.enqueue(2)\n",
" queue.enqueue(3)\n",
" queue.enqueue(4)\n",
"\n",
" print('Test: Dequeue a queue with more than one element')\n",
" assert_equal(queue.dequeue(), 2)\n",
" assert_equal(queue.dequeue(), 3)\n",
" assert_equal(queue.dequeue(), 4)\n",
" \n",
" print('Success: test_end_to_end')\n",
"\n",
"def main():\n",
" test = TestQueue()\n",
" test.test_end_to_end()\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/coding-challenges/blob/master/stacks_queues/queue_list/queue_list_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
}

66
stacks_queues/queue_list/queue_list_solution.ipynb
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@@ -4,7 +4,14 @@
"cell_type": "markdown", "cell_type": "markdown",
"metadata": {}, "metadata": {},
"source": [ "source": [
"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>" "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges).</i></small>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Solution Notebook"
] ]
}, },
{ {
@@ -27,11 +34,13 @@
"source": [ "source": [
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n", "*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
"\n", "\n",
"* If there is one item in the list, do you expect the first and last pointers to both point to it?\n", "* If there is one item in the list, do you expect the first and last pointers to both point to it?\n",
" * Yes\n", " * Yes\n",
"* If there are no items on the list, do you expect the first and last pointers to be NULL?\n", "* If there are no items on the list, do you expect the first and last pointers to be NULL?\n",
" * Yes\n",
"* If you dequeue on an empty queue, does that return None?\n",
" * Yes" " * Yes"
] ]
}, },
@@ -48,7 +57,7 @@
"\n", "\n",
"### Dequeue\n", "### Dequeue\n",
"\n", "\n",
"* Dequeue an empty queue\n", "* Dequeue an empty queue -> None\n",
"* Dequeue a queue with one element\n", "* Dequeue a queue with one element\n",
"* Dequeue a queue with more than one element" "* Dequeue a queue with more than one element"
] ]
@@ -109,15 +118,14 @@
], ],
"source": [ "source": [
"%%writefile queue_list.py\n", "%%writefile queue_list.py\n",
"# Need to avoid naming this queue.py as it \n",
"# will conflict with IPython Notebook\n",
"\n",
"class Node(object):\n", "class Node(object):\n",
" \n",
" def __init__(self, data):\n", " def __init__(self, data):\n",
" self.data = data\n", " self.data = data\n",
" self.next = None\n", " self.next = None\n",
"\n", "\n",
"class Queue(object):\n", "class Queue(object):\n",
" \n",
" def __init__(self):\n", " def __init__(self):\n",
" self.first = None\n", " self.first = None\n",
" self.last = None\n", " self.last = None\n",
@@ -164,8 +172,7 @@
"metadata": {}, "metadata": {},
"source": [ "source": [
"## Unit Test\n", "## Unit Test\n",
"\n", "\n"
"*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand. You generally will not be asked to write a unit test like what is shown below.*"
] ]
}, },
{ {
@@ -179,19 +186,17 @@
"name": "stdout", "name": "stdout",
"output_type": "stream", "output_type": "stream",
"text": [ "text": [
"Test: Dequeue an empty queue\n", "Overwriting test_queue_list.py\n"
"Test: Enqueue to an empty queue\n",
"Test: Dequeue a queue with one element\n",
"Test: Enqueue to a non-empty queue\n",
"Test: Dequeue a queue with more than one element\n",
"Success: test_end_to_end\n"
] ]
} }
], ],
"source": [ "source": [
"%%writefile test_queue_list.py\n",
"from nose.tools import assert_equal\n", "from nose.tools import assert_equal\n",
"\n", "\n",
"class Test(object):\n", "\n",
"class TestQueue(object):\n",
" \n",
" # TODO: It would be better if we had unit tests for each\n", " # TODO: It would be better if we had unit tests for each\n",
" # method in addition to the following end-to-end test\n", " # method in addition to the following end-to-end test\n",
" def test_end_to_end(self):\n", " def test_end_to_end(self):\n",
@@ -217,9 +222,36 @@
" \n", " \n",
" print('Success: test_end_to_end')\n", " print('Success: test_end_to_end')\n",
"\n", "\n",
"def main():\n",
" test = TestQueue()\n",
" test.test_end_to_end()\n",
" \n",
"if __name__ == '__main__':\n", "if __name__ == '__main__':\n",
" test = Test()\n", " main()"
" test.test_end_to_end()" ]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Test: Dequeue an empty queue\n",
"Test: Enqueue to an empty queue\n",
"Test: Dequeue a queue with one element\n",
"Test: Enqueue to a non-empty queue\n",
"Test: Dequeue a queue with more than one element\n",
"Success: test_end_to_end\n"
]
}
],
"source": [
"%run -i test_queue_list.py"
] ]
}, },
{ {

36
stacks_queues/queue_list/test_queue_list.py Normal file
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@@ -0,0 +1,36 @@
from nose.tools import assert_equal
class TestQueue(object):
# TODO: It would be better if we had unit tests for each
# method in addition to the following end-to-end test
def test_end_to_end(self):
print('Test: Dequeue an empty queue')
queue = Queue()
assert_equal(queue.dequeue(), None)
print('Test: Enqueue to an empty queue')
queue.enqueue(1)
print('Test: Dequeue a queue with one element')
assert_equal(queue.dequeue(), 1)
print('Test: Enqueue to a non-empty queue')
queue.enqueue(2)
queue.enqueue(3)
queue.enqueue(4)
print('Test: Dequeue a queue with more than one element')
assert_equal(queue.dequeue(), 2)
assert_equal(queue.dequeue(), 3)
assert_equal(queue.dequeue(), 4)
print('Success: test_end_to_end')
def main():
test = TestQueue()
test.test_end_to_end()
if __name__ == '__main__':
main()