mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Add longest substring k distinct challenge
This commit is contained in:
Donne Martin
parent
391e814d2b
commit
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@ -0,0 +1,171 @@
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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 longest substring with at most k distinct characters.\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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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* Can we assume the strings are ASCII?\n",
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" * Yes\n",
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"* Is this case sensitive?\n",
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" * Yes\n",
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"* Is a substring a contiguous block of chars?\n",
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" * Yes\n",
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"* Do we expect an int as a result?\n",
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" * Yes\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 -> TypeError\n",
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"* '', k = 3 -> 0\n",
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"* 'abcabcdefgghiij', k=3 -> 6\n",
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"* 'abcabcdefgghighij', k=3 -> 7"
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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 Solution(object):\n",
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"\n",
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" def longest_substr(self, string, 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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"**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_longest_substr.py\n",
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"from nose.tools import assert_equal, assert_raises\n",
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"\n",
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"\n",
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"class TestSolution(object):\n",
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"\n",
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" def test_longest_substr(self):\n",
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" solution = Solution()\n",
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" assert_raises(TypeError, solution.longest_substr, None)\n",
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" assert_equal(solution.longest_substr('', k=3), 0)\n",
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" assert_equal(solution.longest_substr('abcabcdefgghiij', k=3), 6)\n",
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" assert_equal(solution.longest_substr('abcabcdefgghighij', k=3), 7)\n",
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" print('Success: test_longest_substr')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestSolution()\n",
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" test.test_longest_substr()\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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@ -0,0 +1,208 @@
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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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"# 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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"## Problem: Find the length longest substring with at most k distinct characters.\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)"
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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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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* Can we assume the strings are ASCII?\n",
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" * Yes\n",
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"* Is this case sensitive?\n",
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" * Yes\n",
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"* Is a substring a contiguous block of chars?\n",
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" * Yes\n",
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"* Do we expect an int as a result?\n",
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" * Yes\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 -> TypeError\n",
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"* '', k = 3 -> 0\n",
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"* 'abcabcdefgghiij', k=3 -> 6\n",
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"* 'abcabcdefgghighij', k=3 -> 7"
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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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"We'll use a `chars_to_index_map` dictionary: char (key) to index (val) map to maintain a sliding window.\n",
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"\n",
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"The index (val) will keep track of the character index in the input string.\n",
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"\n",
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"For each character in the string:\n",
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"\n",
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"* Add the char (key) and index (value) to the map\n",
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"* If the length of our map is greater than k, then we'll need to eliminate one item\n",
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" * Scan the map to find the lowest index and remove it\n",
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" * The new lowest index will therefore be incremented by 1\n",
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"* The max length will be the current index minus the lower index + 1\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n*k), where n is the number of chars, k is the length of the map due to the min() call\n",
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"* Space: 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": 1,
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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 Solution(object):\n",
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"\n",
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" def longest_substr(self, string, k):\n",
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" if not isinstance(string, str):\n",
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" raise TypeError('string must be of type str')\n",
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" if not isinstance(k, int):\n",
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" raise TypeError('k must be of type int')\n",
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" low_index = 0\n",
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" max_length = 0\n",
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" chars_to_index_map = {}\n",
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" for index, char in enumerate(string):\n",
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" chars_to_index_map[char] = index\n",
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" if len(chars_to_index_map) > k:\n",
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" low_index = min(chars_to_index_map.values())\n",
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" del chars_to_index_map[string[low_index]]\n",
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" low_index += 1\n",
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" max_length = max(max_length, index - low_index + 1)\n",
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" return max_length"
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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": "code",
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"execution_count": 2,
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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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"Overwriting test_longest_substr.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_longest_substr.py\n",
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"from nose.tools import assert_equal, assert_raises\n",
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"\n",
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"\n",
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"class TestSolution(object):\n",
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"\n",
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" def test_longest_substr(self):\n",
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" solution = Solution()\n",
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" assert_raises(TypeError, solution.longest_substr, None)\n",
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" assert_equal(solution.longest_substr('', k=3), 0)\n",
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" assert_equal(solution.longest_substr('abcabcdefgghiij', k=3), 6)\n",
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" assert_equal(solution.longest_substr('abcabcdefgghighij', k=3), 7)\n",
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" print('Success: test_longest_substr')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestSolution()\n",
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" test.test_longest_substr()\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": "code",
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"execution_count": 3,
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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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"Success: test_longest_substr\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_longest_substr.py"
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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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@ -0,0 +1,21 @@
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from nose.tools import assert_equal, assert_raises
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class TestSolution(object):
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def test_longest_substr(self):
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solution = Solution()
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assert_raises(TypeError, solution.longest_substr, None)
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assert_equal(solution.longest_substr('', k=3), 0)
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assert_equal(solution.longest_substr('abcabcdefgghiij', k=3), 6)
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assert_equal(solution.longest_substr('abcabcdefgghighij', k=3), 7)
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print('Success: test_longest_substr')
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def main():
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test = TestSolution()
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test.test_longest_substr()
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if __name__ == '__main__':
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main()
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