Add longest substr k distinct challenge

online_judges/longest_substr_k_distinct/longest_substr_challenge.ipynb

@@ -0,0 +1,171 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "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)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Challenge Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Find the length of the longest substring with at most k distinct characters.\n",
+    "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)\n",
+    "* [Solution Notebook](#Solution-Notebook)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "* Can we assume the inputs are valid?\n",
+    "    * No\n",
+    "* Can we assume the strings are ASCII?\n",
+    "    * Yes\n",
+    "* Is this case sensitive?\n",
+    "    * Yes\n",
+    "* Is a substring a contiguous block of chars?\n",
+    "    * Yes\n",
+    "* Do we expect an int as a result?\n",
+    "    * Yes\n",
+    "* Can we assume this fits memory?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* None -> TypeError\n",
+    "* '', k = 3 -> 0\n",
+    "* 'abcabcdefgghiij', k=3 -> 6\n",
+    "* 'abcabcdefgghighij', k=3 -> 7"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "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."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "class Solution(object):\n",
+    "\n",
+    "    def longest_substr(self, string, k):\n",
+    "        # TODO: Implement me\n",
+    "        pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**The following unit test is expected to fail until you solve the challenge.**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "# %load test_longest_substr.py\n",
+    "from nose.tools import assert_equal, assert_raises\n",
+    "\n",
+    "\n",
+    "class TestSolution(object):\n",
+    "\n",
+    "    def test_longest_substr(self):\n",
+    "        solution = Solution()\n",
+    "        assert_raises(TypeError, solution.longest_substr, None)\n",
+    "        assert_equal(solution.longest_substr('', k=3), 0)\n",
+    "        assert_equal(solution.longest_substr('abcabcdefgghiij', k=3), 6)\n",
+    "        assert_equal(solution.longest_substr('abcabcdefgghighij', k=3), 7)\n",
+    "        print('Success: test_longest_substr')\n",
+    "\n",
+    "\n",
+    "def main():\n",
+    "    test = TestSolution()\n",
+    "    test.test_longest_substr()\n",
+    "\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Solution Notebook\n",
+    "\n",
+    "Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
+   ]
+  }
+ ],
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