mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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117 lines
2.8 KiB
Plaintext
117 lines
2.8 KiB
Plaintext
{
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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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"## Problem: Determine if a string s1 is a rotation of another string s2. Also write a function is_substring which you can only call once to determine whether a rotation occurs\n",
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"\n",
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"* [Clarifying Questions](#Clarifying-Questions)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)"
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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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"## Clarifying Questions\n",
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"\n",
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"* Is the string ASCII (extended)? Or Unicode?\n",
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" * ASCII extended, which is 256 characters\n",
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"* Can you use additional data structures? \n",
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" * Yes\n",
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"* Is this case sensitive?\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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"* Any strings that differ in size results in False\n",
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"* NULL, 'foo' -> False (any NULL results in False)\n",
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"* ' ', 'foo' -> False\n",
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"* ' ', ' ' -> True\n",
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"* 'foobarbaz', 'barbazfoo' -> True"
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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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"Using the following test case:\n",
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"* s1 = 'barbazfoo'\n",
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"* s2 = 'foobarbaz'\n",
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"\n",
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"We see that if we can use the given is_substring method if we take compare s2 with s1 + s1:\n",
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"* s2 = 'foobarbaz'\n",
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"* s3 = 'barbaz*foobarbaz*foo'\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: O(2n) of additional space for s3, which reduces to O(n)"
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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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"def is_substring(s1, s2):\n",
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" return s1 in s2\n",
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"\n",
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"def is_rotation(s1, s2):\n",
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" if s1 is None or s2 is None:\n",
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" return False\n",
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" if len(s1) != len(s2):\n",
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" return False\n",
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" s3 = s1 + s1\n",
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" return is_substring(s2, s3)\n",
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"\n",
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"print(is_rotation('o', 'oo'))\n",
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"print(is_rotation(None, 'foo'))\n",
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"print(is_rotation('', 'foo'))\n",
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"print(is_rotation('', ''))\n",
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"print(is_rotation('foobarbaz', 'barbazfoo'))"
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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": "2.7.9"
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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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