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Added kth to last element challenge.

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Donne Martin 2015-07-02 23:10:31 -04:00
parent 836749c98e
commit f530111970
4 changed files with 277 additions and 22 deletions
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0
linked_lists/kth_to_last_elem/__init__.py Normal file
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linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb Normal file
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@ -0,0 +1,197 @@
{
"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: Find the kth to last element of a linked list\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",
"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
"\n",
"* Can we assume k is a valid integer?\n",
" * Yes\n",
"* If k = 0, does this return the last element?\n",
" * Yes\n",
"* What happens if k is greater than or equal to the length of the linked list?\n",
" * Return None\n",
"* Can you use additional data structures?\n",
" * No\n",
"* Can we assume we already have a linked list class that can be used for this problem?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"* Empty list -> None\n",
"* k is >= the length of the linked list -> None\n",
"* One element, k = 0 -> element\n",
"* General case with many elements, k < length of linked list"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/linked_lists/kth_to_last_elem/kth_to_last_elem_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": [
"%run ../linked_list/linked_list.py\n",
"%load ../linked_list/linked_list.py"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"class MyLinkedList(LinkedList):\n",
" \n",
" def kth_to_last_elem(self, k):\n",
" # TODO: Implement me\n",
" pass"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"\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_kth_to_last_elem.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class Test(object):\n",
" \n",
" def test_kth_to_last_elem(self):\n",
" print('Test: Empty list')\n",
" linked_list = MyLinkedList(None)\n",
" assert_equal(linked_list.kth_to_last_elem(0), None)\n",
" \n",
" print('Test: k >= len(list)')\n",
" assert_equal(linked_list.kth_to_last_elem(100), None)\n",
" \n",
" print('Test: One element, k = 0')\n",
" head = Node(2)\n",
" linked_list = MyLinkedList(head)\n",
" assert_equal(linked_list.kth_to_last_elem(0), 2)\n",
" \n",
" print('Test: General case')\n",
" linked_list.insert_to_front(1)\n",
" linked_list.insert_to_front(3)\n",
" linked_list.insert_to_front(5)\n",
" linked_list.insert_to_front(7)\n",
" assert_equal(linked_list.kth_to_last_elem(2), 3)\n",
" \n",
" print('Success: test_kth_to_last_elem')\n",
"\n",
"def main():\n",
" test = Test()\n",
" test.test_kth_to_last_elem()\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/linked_lists/kth_to_last_elem/kth_to_last_elem_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
}

69
linked_lists/kth_to_last_elem/kth_to_last_elem_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"
] ]
}, },
{ {
@ -26,7 +33,7 @@
"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",
"* Can we assume k is a valid integer?\n", "* Can we assume k is a valid integer?\n",
" * Yes\n", " * Yes\n",
@ -46,10 +53,9 @@
"source": [ "source": [
"## Test Cases\n", "## Test Cases\n",
"\n", "\n",
"* Empty list\n", "* Empty list -> None\n",
"* k is not an integer\n", "* k is >= the length of the linked list -> None\n",
"* k is >= the length of the linked list\n", "* One element, k = 0 -> element\n",
"* One element, k = 0\n",
"* General case with many elements, k < length of linked list" "* General case with many elements, k < length of linked list"
] ]
}, },
@ -80,11 +86,11 @@
"cell_type": "code", "cell_type": "code",
"execution_count": 1, "execution_count": 1,
"metadata": { "metadata": {
"collapsed": true "collapsed": false
}, },
"outputs": [], "outputs": [],
"source": [ "source": [
"%run linked_list.py" "%run ../linked_list/linked_list.py"
] ]
}, },
{ {
@ -96,6 +102,7 @@
"outputs": [], "outputs": [],
"source": [ "source": [
"class MyLinkedList(LinkedList):\n", "class MyLinkedList(LinkedList):\n",
" \n",
" def kth_to_last_elem(self, k):\n", " def kth_to_last_elem(self, k):\n",
" if self.head is None:\n", " if self.head is None:\n",
" return\n", " return\n",
@ -127,13 +134,6 @@
"## Unit Test" "## Unit Test"
] ]
}, },
{
"cell_type": "markdown",
"metadata": {},
"source": [
"*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.*"
]
},
{ {
"cell_type": "code", "cell_type": "code",
"execution_count": 3, "execution_count": 3,
@ -145,18 +145,17 @@
"name": "stdout", "name": "stdout",
"output_type": "stream", "output_type": "stream",
"text": [ "text": [
"Test: Empty list\n", "Overwriting test_kth_to_last_elem.py\n"
"Test: k >= len(list)\n",
"Test: One element, k = 0\n",
"Test: General case\n",
"Success: test_kth_to_last_elem\n"
] ]
} }
], ],
"source": [ "source": [
"%%writefile test_kth_to_last_elem.py\n",
"from nose.tools import assert_equal\n", "from nose.tools import assert_equal\n",
"\n", "\n",
"\n",
"class Test(object):\n", "class Test(object):\n",
" \n",
" def test_kth_to_last_elem(self):\n", " def test_kth_to_last_elem(self):\n",
" print('Test: Empty list')\n", " print('Test: Empty list')\n",
" linked_list = MyLinkedList(None)\n", " linked_list = MyLinkedList(None)\n",
@ -179,9 +178,35 @@
" \n", " \n",
" print('Success: test_kth_to_last_elem')\n", " print('Success: test_kth_to_last_elem')\n",
"\n", "\n",
"if __name__ == '__main__':\n", "def main():\n",
" test = Test()\n", " test = Test()\n",
" test.test_kth_to_last_elem()" " test.test_kth_to_last_elem()\n",
" \n",
"if __name__ == '__main__':\n",
" main()"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Test: Empty list\n",
"Test: k >= len(list)\n",
"Test: One element, k = 0\n",
"Test: General case\n",
"Success: test_kth_to_last_elem\n"
]
}
],
"source": [
"%run -i test_kth_to_last_elem.py"
] ]
} }
], ],

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linked_lists/kth_to_last_elem/test_kth_to_last_elem.py Normal file
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@ -0,0 +1,33 @@
from nose.tools import assert_equal
class Test(object):
def test_kth_to_last_elem(self):
print('Test: Empty list')
linked_list = MyLinkedList(None)
assert_equal(linked_list.kth_to_last_elem(0), None)
print('Test: k >= len(list)')
assert_equal(linked_list.kth_to_last_elem(100), None)
print('Test: One element, k = 0')
head = Node(2)
linked_list = MyLinkedList(head)
assert_equal(linked_list.kth_to_last_elem(0), 2)
print('Test: General case')
linked_list.insert_to_front(1)
linked_list.insert_to_front(3)
linked_list.insert_to_front(5)
linked_list.insert_to_front(7)
assert_equal(linked_list.kth_to_last_elem(2), 3)
print('Success: test_kth_to_last_elem')
def main():
test = Test()
test.test_kth_to_last_elem()
if __name__ == '__main__':
main()