Added hash map challenge.

arrays_strings/hash_map/hash_map_challenge.ipynb

@@ -0,0 +1,217 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<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>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Challenge Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Implement a hash table with set, get, and remove methods.\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",
+    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "\n",
+    "* For simplicity, are the keys integers only?\n",
+    "    * Yes\n",
+    "* For collision resolution, can we use linked lists?\n",
+    "    * Yes\n",
+    "* Do we have to worry about load factors?\n",
+    "    * No"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* get on an empty hash table index\n",
+    "* set on an empty hash table index\n",
+    "* set on a non empty hash table index\n",
+    "* set on a key that already exists\n",
+    "* remove on a key with an entry\n",
+    "* remove on a key without an entry"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb).  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 Item(object):\n",
+    "    \n",
+    "    def __init__(self, key, value):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "class HashTable(object):\n",
+    "    \n",
+    "    def __init__(self, size):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def hash_function(self, key):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def set(self, key, value):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def get(self, key):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def remove(self, key):\n",
+    "        # TODO: Implement me\n",
+    "        pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "\n",
+    "\n",
+    "**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_hash_map.py\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestHashMap(object):\n",
+    "    \n",
+    "    # TODO: It would be better if we had unit tests for each\n",
+    "    # method in addition to the following end-to-end test\n",
+    "    def test_end_to_end(self):\n",
+    "        hash_table = HashTable(10)\n",
+    "        \n",
+    "        print(\"Test: get on an empty hash table index\")\n",
+    "        assert_equal(hash_table.get(0), None)\n",
+    "        \n",
+    "        print(\"Test: set on an empty hash table index\")\n",
+    "        hash_table.set(0, 'foo')\n",
+    "        assert_equal(hash_table.get(0), 'foo')\n",
+    "        hash_table.set(1, 'bar')\n",
+    "        assert_equal(hash_table.get(1), 'bar')\n",
+    "        \n",
+    "        print(\"Test: set on a non empty hash table index\")\n",
+    "        hash_table.set(10, 'foo2')\n",
+    "        assert_equal(hash_table.get(0), 'foo')\n",
+    "        assert_equal(hash_table.get(10), 'foo2')\n",
+    "        \n",
+    "        print(\"Test: set on a key that already exists\")\n",
+    "        hash_table.set(10, 'foo3')\n",
+    "        assert_equal(hash_table.get(0), 'foo')\n",
+    "        assert_equal(hash_table.get(10), 'foo3')\n",
+    "        \n",
+    "        print(\"Test: remove on a key that already exists\")\n",
+    "        hash_table.remove(10)\n",
+    "        assert_equal(hash_table.get(0), 'foo')\n",
+    "        assert_equal(hash_table.get(10), None)\n",
+    "        \n",
+    "        print(\"Test: remove on a key that doesn't exist\")\n",
+    "        hash_table.remove(-1)\n",
+    "        \n",
+    "        print('Success: test_end_to_end')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestHashMap()\n",
+    "    test.test_end_to_end()\n",
+    "    \n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Solution Notebook\n",
+    "\n",
+    "Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/arrays_strings/hash_map/hash_map_solution.ipynb) for a discussion on algorithms and code solutions."
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.10"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}

arrays_strings/hash_map/hash_map_solution.ipynb

@@ -4,7 +4,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "<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>"
+    "<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>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Solution Notebook"
    ]
   },
   {
@@ -17,7 +24,6 @@
     "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
     "* [Code](#Code)\n",
-    "* [Pythonic-Code](#Pythonic-Code)\n",
     "* [Unit Test](#Unit-Test)"
    ]
   },
@@ -27,7 +33,7 @@
    "source": [
     "## Constraints\n",
     "\n",
-    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
     "\n",
     "* For simplicity, are the keys integers only?\n",
     "    * Yes\n",
@@ -111,11 +117,13 @@
    "outputs": [],
    "source": [
     "class Item(object):\n",
+    "    \n",
     "    def __init__(self, key, value):\n",
     "        self.key = key\n",
     "        self.value = value\n",
     "\n",
     "class HashTable(object):\n",
+    "    \n",
     "    def __init__(self, size):\n",
     "        self.size = size\n",
     "        self.table = [[] for _ in xrange(self.size)]\n",
@@ -152,13 +160,6 @@
     "## Unit Test"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "*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.*"
-   ]
-  },
   {
    "cell_type": "code",
    "execution_count": 2,
@@ -170,20 +171,17 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Test: get on an empty hash table index\n",
+      "Overwriting test_hash_map.py\n"
-      "Test: set on an empty hash table index\n",
-      "Test: set on a non empty hash table index\n",
-      "Test: set on a key that already exists\n",
-      "Test: remove on a key that already exists\n",
-      "Test: remove on a key that doesn't exist\n",
-      "Success: test_end_to_end\n"
      ]
     }
    ],
    "source": [
+    "%%writefile test_hash_map.py\n",
     "from nose.tools import assert_equal\n",
     "\n",
-    "class Test(object):\n",
+    "\n",
+    "class TestHashMap(object):\n",
+    "    \n",
     "    # TODO: It would be better if we had unit tests for each\n",
     "    # method in addition to the following end-to-end test\n",
     "    def test_end_to_end(self):\n",
@@ -218,9 +216,37 @@
     "        \n",
     "        print('Success: test_end_to_end')\n",
     "\n",
+    "def main():\n",
+    "    test = TestHashMap()\n",
+    "    test.test_end_to_end()\n",
+    "    \n",
     "if __name__ == '__main__':\n",
-    "    test = Test()\n",
+    "    main()"
-    "    test.test_end_to_end()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: get on an empty hash table index\n",
+      "Test: set on an empty hash table index\n",
+      "Test: set on a non empty hash table index\n",
+      "Test: set on a key that already exists\n",
+      "Test: remove on a key that already exists\n",
+      "Test: remove on a key that doesn't exist\n",
+      "Success: test_end_to_end\n"
+     ]
+    }
+   ],
+   "source": [
+    "run -i test_hash_map.py"
    ]
   }
  ],

arrays_strings/hash_map/test_hash_map.py

@@ -0,0 +1,45 @@
+from nose.tools import assert_equal
+
+
+class TestHashMap(object):
+    
+    # TODO: It would be better if we had unit tests for each
+    # method in addition to the following end-to-end test
+    def test_end_to_end(self):
+        hash_table = HashTable(10)
+        
+        print("Test: get on an empty hash table index")
+        assert_equal(hash_table.get(0), None)
+        
+        print("Test: set on an empty hash table index")
+        hash_table.set(0, 'foo')
+        assert_equal(hash_table.get(0), 'foo')
+        hash_table.set(1, 'bar')
+        assert_equal(hash_table.get(1), 'bar')
+        
+        print("Test: set on a non empty hash table index")
+        hash_table.set(10, 'foo2')
+        assert_equal(hash_table.get(0), 'foo')
+        assert_equal(hash_table.get(10), 'foo2')
+        
+        print("Test: set on a key that already exists")
+        hash_table.set(10, 'foo3')
+        assert_equal(hash_table.get(0), 'foo')
+        assert_equal(hash_table.get(10), 'foo3')
+        
+        print("Test: remove on a key that already exists")
+        hash_table.remove(10)
+        assert_equal(hash_table.get(0), 'foo')
+        assert_equal(hash_table.get(10), None)
+        
+        print("Test: remove on a key that doesn't exist")
+        hash_table.remove(-1)
+        
+        print('Success: test_end_to_end')
+
+def main():
+    test = TestHashMap()
+    test.test_end_to_end()
+    
+if __name__ == '__main__':
+    main()