mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Added find loop start challenge.
This commit is contained in:
Donne Martin
parent
4c2c1d4391
commit
836749c98e
0
linked_lists/find_loop_start/__init__.py
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0
linked_lists/find_loop_start/__init__.py
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209
linked_lists/find_loop_start/find_loop_start_challenge.ipynb
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209
linked_lists/find_loop_start/find_loop_start_challenge.ipynb
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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 start of a linked list loop.\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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"* Is this a singly linked list?\n",
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" * Yes\n",
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"* Can we assume we are always passed a circular linked list?\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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"* Not a circular linked list -> None\n",
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" * One element\n",
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" * Two elements\n",
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" * Three or more elements\n",
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"* General case"
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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/find_loop_start/find_loop_start_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 ../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 find_loop_start(self):\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_find_loop_start.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 TestFindLoopStart(object):\n",
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" \n",
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" def test_find_loop_start(self):\n",
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" print('Test: Empty list')\n",
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" linked_list = MyLinkedList()\n",
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" assert_equal(linked_list.find_loop_start(), None)\n",
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" \n",
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" print('Test: Not a circular linked list: One element')\n",
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" head = Node(1)\n",
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" linked_list = MyLinkedList(head)\n",
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" assert_equal(linked_list.find_loop_start(), None)\n",
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" \n",
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" print('Test: Not a circular linked list: Two elements')\n",
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" linked_list.append(2)\n",
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" assert_equal(linked_list.find_loop_start(), None)\n",
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" \n",
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" print('Test: Not a circular linked list: Three or more elements')\n",
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" linked_list.append(3)\n",
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" assert_equal(linked_list.find_loop_start(), None)\n",
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" \n",
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" print('Test: General case: Circular linked list')\n",
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" node10 = Node(10)\n",
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" node9 = Node(9, node10)\n",
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" node8 = Node(8, node9)\n",
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" node7 = Node(7, node8)\n",
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" node6 = Node(6, node7)\n",
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" node5 = Node(5, node6)\n",
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" node4 = Node(4, node5)\n",
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" node3 = Node(3, node4)\n",
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" node2 = Node(2, node3)\n",
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" node1 = Node(1, node2)\n",
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" node0 = Node(0, node1)\n",
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" node10.next = node3\n",
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" linked_list = MyLinkedList(node0)\n",
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" assert_equal(linked_list.find_loop_start(), 3)\n",
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" \n",
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" print('Success: test_find_loop_start')\n",
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"\n",
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"def main():\n",
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" test = TestFindLoopStart()\n",
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" test.test_find_loop_start()\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/find_loop_start/find_loop_start_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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@ -26,9 +33,9 @@
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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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"* This is a singly linked list?\n",
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"* Is this a singly linked list?\n",
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" * Yes\n",
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"* Can we assume we are always passed a circular linked list?\n",
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" * No\n",
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@ -42,8 +49,8 @@
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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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"* Not a circular linked list\n",
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"* Empty list -> None\n",
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"* Not a circular linked list -> None\n",
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" * One element\n",
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" * Two elements\n",
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" * Three or more elements\n",
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@ -84,7 +91,7 @@
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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 +103,7 @@
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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 find_loop_start(self):\n",
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" if self.head is None or self.head.next is None:\n",
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" return\n",
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@ -130,13 +138,6 @@
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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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@ -148,19 +149,17 @@
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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: Not a circular linked list: One element\n",
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"Test: Not a circular linked list: Two elements\n",
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"Test: Not a circular linked list: Three or more elements\n",
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"Test: General case: Circular linked list\n",
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"Success: test_find_loop_start\n"
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"Overwriting test_find_loop_start.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_find_loop_start.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"class Test(object):\n",
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"\n",
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"class TestFindLoopStart(object):\n",
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" \n",
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" def test_find_loop_start(self):\n",
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" print('Test: Empty list')\n",
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" linked_list = MyLinkedList()\n",
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@ -197,9 +196,36 @@
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" \n",
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" print('Success: test_find_loop_start')\n",
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"\n",
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"def main():\n",
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" test = TestFindLoopStart()\n",
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" test.test_find_loop_start()\n",
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" \n",
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"if __name__ == '__main__':\n",
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" test = Test()\n",
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" test.test_find_loop_start()"
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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: Not a circular linked list: One element\n",
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"Test: Not a circular linked list: Two elements\n",
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"Test: Not a circular linked list: Three or more elements\n",
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"Test: General case: Circular linked list\n",
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"Success: test_find_loop_start\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_find_loop_start.py"
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]
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}
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],
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47
linked_lists/find_loop_start/test_find_loop_start.py
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linked_lists/find_loop_start/test_find_loop_start.py
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from nose.tools import assert_equal
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class TestFindLoopStart(object):
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def test_find_loop_start(self):
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print('Test: Empty list')
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linked_list = MyLinkedList()
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assert_equal(linked_list.find_loop_start(), None)
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print('Test: Not a circular linked list: One element')
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head = Node(1)
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linked_list = MyLinkedList(head)
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assert_equal(linked_list.find_loop_start(), None)
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print('Test: Not a circular linked list: Two elements')
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linked_list.append(2)
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assert_equal(linked_list.find_loop_start(), None)
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print('Test: Not a circular linked list: Three or more elements')
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linked_list.append(3)
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assert_equal(linked_list.find_loop_start(), None)
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print('Test: General case: Circular linked list')
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node10 = Node(10)
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node9 = Node(9, node10)
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node8 = Node(8, node9)
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node7 = Node(7, node8)
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node6 = Node(6, node7)
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node5 = Node(5, node6)
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node4 = Node(4, node5)
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node3 = Node(3, node4)
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node2 = Node(2, node3)
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node1 = Node(1, node2)
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node0 = Node(0, node1)
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node10.next = node3
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linked_list = MyLinkedList(node0)
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assert_equal(linked_list.find_loop_start(), 3)
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print('Success: test_find_loop_start')
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def main():
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test = TestFindLoopStart()
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test.test_find_loop_start()
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if __name__ == '__main__':
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main()
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