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https://github.com/donnemartin/interactive-coding-challenges
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Add magic index challenge
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Donne Martin
196
recursion_dynamic/magic_index/magic_index_challenge.ipynb
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196
recursion_dynamic/magic_index/magic_index_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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"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)."
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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 magic index in an array, where array[i] = i.\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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"* Is the array sorted?\n",
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" * Yes\n",
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"* Are the elements in the array distinct?\n",
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" * No\n",
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"* Does a magic index always exist?\n",
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" * No\n",
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"* If there is no magic index, do we just return -1?\n",
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" * Yes\n",
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"* Are negative values allowed in the array?\n",
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" * Yes\n",
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"* If there are multiple magic values, what do we return?\n",
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" * Return the left-most one\n",
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"* Can we assume this fits memory?\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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"* None input -> -1\n",
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"* Empty array -> -1\n",
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"\n",
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"<pre>\n",
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"a[i] -4 -2 2 6 6 6 6 10\n",
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" i 0 1 2 3 4 5 6 7\n",
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"</pre>\n",
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"\n",
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"Result: 2\n",
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"\n",
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"<pre>\n",
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"a[i] -4 -2 1 6 6 6 6 10\n",
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" i 0 1 2 3 4 5 6 7\n",
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"</pre>\n",
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"\n",
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"Result: 6\n",
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"\n",
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"<pre>\n",
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"a[i] -4 -2 1 6 6 6 7 10\n",
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" i 0 1 2 3 4 5 6 7\n",
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"</pre>\n",
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"\n",
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"Result: -1"
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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](). 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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"class MagicIndex(object):\n",
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"\n",
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" def find_magic_index(self, array):\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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"**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_magic_index.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 TestFindMagicIndex(object):\n",
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"\n",
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" def test_find_magic_index(self):\n",
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" magic_index = MagicIndex()\n",
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" assert_equal(magic_index.find_magic_index(None), -1)\n",
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" assert_equal(magic_index.find_magic_index([]), -1)\n",
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" array = [-4, -2, 2, 6, 6, 6, 6, 10]\n",
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" assert_equal(magic_index.find_magic_index(array), 2)\n",
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" array = [-4, -2, 1, 6, 6, 6, 6, 10]\n",
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" assert_equal(magic_index.find_magic_index(array), 6)\n",
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" array = [-4, -2, 1, 6, 6, 6, 7, 10]\n",
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" assert_equal(magic_index.find_magic_index(array), -1)\n",
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" print('Success: test_find_magic')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestFindMagicIndex()\n",
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" test.test_find_magic_index()\n",
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"\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]() 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 3",
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"language": "python",
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"name": "python3"
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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": 3
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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": "ipython3",
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"version": "3.5.0"
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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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