mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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Added kth to last element challenge.
This commit is contained in:
Donne Martin
parent
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commit
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0
linked_lists/kth_to_last_elem/__init__.py
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0
linked_lists/kth_to_last_elem/__init__.py
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197
linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb
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197
linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb
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@ -0,0 +1,197 @@
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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](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/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: Find the kth to last element of a linked list\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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"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
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"\n",
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"* Can we assume k is a valid integer?\n",
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" * Yes\n",
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"* If k = 0, does this return the last element?\n",
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" * Yes\n",
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"* What happens if k is greater than or equal to the length of the linked list?\n",
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" * Return None\n",
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"* Can you use additional data structures?\n",
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" * No\n",
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"* Can we assume we already have a linked list class that can be used for this problem?\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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"* Empty list -> None\n",
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"* k is >= the length of the linked list -> None\n",
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"* One element, k = 0 -> element\n",
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"* General case with many elements, k < length of linked list"
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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/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."
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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": false
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},
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"outputs": [],
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"source": [
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"%run ../linked_list/linked_list.py\n",
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"%load ../linked_list/linked_list.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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"class MyLinkedList(LinkedList):\n",
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" \n",
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" def kth_to_last_elem(self, k):\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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"\n",
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"\n",
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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": false
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},
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"outputs": [],
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"source": [
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"# %load test_kth_to_last_elem.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 Test(object):\n",
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" \n",
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" def test_kth_to_last_elem(self):\n",
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" print('Test: Empty list')\n",
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" linked_list = MyLinkedList(None)\n",
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" assert_equal(linked_list.kth_to_last_elem(0), None)\n",
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" \n",
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" print('Test: k >= len(list)')\n",
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" assert_equal(linked_list.kth_to_last_elem(100), None)\n",
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" \n",
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" print('Test: One element, k = 0')\n",
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" head = Node(2)\n",
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" linked_list = MyLinkedList(head)\n",
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" assert_equal(linked_list.kth_to_last_elem(0), 2)\n",
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" \n",
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" print('Test: General case')\n",
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" linked_list.insert_to_front(1)\n",
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" linked_list.insert_to_front(3)\n",
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" linked_list.insert_to_front(5)\n",
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" linked_list.insert_to_front(7)\n",
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" assert_equal(linked_list.kth_to_last_elem(2), 3)\n",
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" \n",
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" print('Success: test_kth_to_last_elem')\n",
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"\n",
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"def main():\n",
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" test = Test()\n",
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" test.test_kth_to_last_elem()\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/coding-challenges/blob/master/linked_lists/kth_to_last_elem/kth_to_last_elem_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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@ -4,7 +4,14 @@
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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](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
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"<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>"
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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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@ -26,7 +33,7 @@
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"source": [
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"## Constraints\n",
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"\n",
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"*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
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"*Problem statements are sometimes ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
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"\n",
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"* Can we assume k is a valid integer?\n",
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" * Yes\n",
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@ -46,10 +53,9 @@
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"source": [
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"## Test Cases\n",
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"\n",
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"* Empty list\n",
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"* k is not an integer\n",
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"* k is >= the length of the linked list\n",
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"* One element, k = 0\n",
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"* Empty list -> None\n",
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"* k is >= the length of the linked list -> None\n",
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"* One element, k = 0 -> element\n",
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"* General case with many elements, k < length of linked list"
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]
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},
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@ -80,11 +86,11 @@
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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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"collapsed": false
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},
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"outputs": [],
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"source": [
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"%run linked_list.py"
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"%run ../linked_list/linked_list.py"
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]
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},
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{
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@ -96,6 +102,7 @@
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"outputs": [],
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"source": [
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"class MyLinkedList(LinkedList):\n",
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" \n",
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" def kth_to_last_elem(self, k):\n",
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" if self.head is None:\n",
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" return\n",
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@ -127,13 +134,6 @@
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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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"*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.*"
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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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@ -145,18 +145,17 @@
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Test: Empty list\n",
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"Test: k >= len(list)\n",
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"Test: One element, k = 0\n",
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"Test: General case\n",
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"Success: test_kth_to_last_elem\n"
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"Overwriting test_kth_to_last_elem.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_kth_to_last_elem.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 Test(object):\n",
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" \n",
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" def test_kth_to_last_elem(self):\n",
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" print('Test: Empty list')\n",
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" linked_list = MyLinkedList(None)\n",
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@ -179,9 +178,35 @@
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" \n",
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" print('Success: test_kth_to_last_elem')\n",
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"\n",
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"if __name__ == '__main__':\n",
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"def main():\n",
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" test = Test()\n",
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" test.test_kth_to_last_elem()"
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" test.test_kth_to_last_elem()\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": 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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"Test: Empty list\n",
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"Test: k >= len(list)\n",
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"Test: One element, k = 0\n",
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"Test: General case\n",
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"Success: test_kth_to_last_elem\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_kth_to_last_elem.py"
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]
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}
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],
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33
linked_lists/kth_to_last_elem/test_kth_to_last_elem.py
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33
linked_lists/kth_to_last_elem/test_kth_to_last_elem.py
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from nose.tools import assert_equal
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class Test(object):
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def test_kth_to_last_elem(self):
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print('Test: Empty list')
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linked_list = MyLinkedList(None)
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assert_equal(linked_list.kth_to_last_elem(0), None)
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print('Test: k >= len(list)')
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assert_equal(linked_list.kth_to_last_elem(100), None)
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print('Test: One element, k = 0')
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head = Node(2)
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linked_list = MyLinkedList(head)
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assert_equal(linked_list.kth_to_last_elem(0), 2)
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print('Test: General case')
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linked_list.insert_to_front(1)
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linked_list.insert_to_front(3)
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linked_list.insert_to_front(5)
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linked_list.insert_to_front(7)
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assert_equal(linked_list.kth_to_last_elem(2), 3)
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print('Success: test_kth_to_last_elem')
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def main():
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test = Test()
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test.test_kth_to_last_elem()
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if __name__ == '__main__':
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main()
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