Added stack min challenge.

stacks_queues/stack_min/stack_min_challenge.ipynb

@@ -0,0 +1,208 @@
+{
+ "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 stack with push, pop, and min methods running O(1) time.\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",
+    "* Can we assume this is a stack of ints?\n",
+    "    * Yes\n",
+    "* If we call this function on an empty stack, can we return max int?\n",
+    "    * Yes\n",
+    "* Can we assume we already have a stack class that can be used for this problem?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* Push/pop on empty stack\n",
+    "* Push/pop on non-empty stack"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/stacks_queues/stack_min/stack_min_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": true
+   },
+   "outputs": [],
+   "source": [
+    "%run ../stack/stack.py\n",
+    "%load ../stack/stack.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "import sys\n",
+    "\n",
+    "\n",
+    "class MyStack(Stack):\n",
+    "    def __init__(self, top=None):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def min(self):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def push(self, data):\n",
+    "        # TODO: Implement me\n",
+    "        pass\n",
+    "\n",
+    "    def pop(self):\n",
+    "        # TODO: Implement me\n",
+    "        pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test\n",
+    "\n",
+    "\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_stack_min.py\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestStackMin(object):\n",
+    "    def test_stack_min(self):\n",
+    "        print('Test: Push on empty stack, non-empty stack')\n",
+    "        stack = MyStack()\n",
+    "        stack.push(5)\n",
+    "        assert_equal(stack.peek(), 5)\n",
+    "        assert_equal(stack.min(), 5)\n",
+    "        stack.push(1)\n",
+    "        assert_equal(stack.peek(), 1)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        stack.push(3)\n",
+    "        assert_equal(stack.peek(), 3)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        stack.push(0)\n",
+    "        assert_equal(stack.peek(), 0)\n",
+    "        assert_equal(stack.min(), 0)\n",
+    "\n",
+    "        print('Test: Pop on non-empty stack')\n",
+    "        assert_equal(stack.pop(), 0)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        assert_equal(stack.pop(), 3)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        assert_equal(stack.pop(), 1)\n",
+    "        assert_equal(stack.min(), 5)\n",
+    "        assert_equal(stack.pop(), 5)\n",
+    "        assert_equal(stack.min(), sys.maxint)\n",
+    "\n",
+    "        print('Test: Pop empty stack')\n",
+    "        assert_equal(stack.pop(), None)\n",
+    "        \n",
+    "        print('Success: test_stack_min')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestStackMin()\n",
+    "    test.test_stack_min()\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/stacks_queues/stack_min/stack_min_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
+}

stacks_queues/stack_min/stack_min_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"
    ]
   },
   {
@@ -26,10 +33,12 @@
    "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",
     "* Can we assume this is a stack of ints?\n",
     "    * Yes\n",
+    "* If we call this function on an empty stack, can we return max int?\n",
+    "    * Yes\n",
     "* Can we assume we already have a stack class that can be used for this problem?\n",
     "    * Yes"
    ]
@@ -98,7 +107,7 @@
    },
    "outputs": [],
    "source": [
-    "%run stack.py"
+    "%run ../stack/stack.py"
    ]
   },
   {
@@ -111,6 +120,7 @@
    "source": [
     "import sys\n",
     "\n",
+    "\n",
     "class MyStack(Stack):\n",
     "    def __init__(self, top=None):\n",
     "        self.min_vals = Stack()\n",
@@ -139,8 +149,7 @@
    "metadata": {},
    "source": [
     "## Unit Test\n",
-    "\n",
+    "\n"
-    "*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.*"
    ]
   },
   {
@@ -154,17 +163,16 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Test: Push on empty stack, non-empty stack\n",
+      "Overwriting test_stack_min.py\n"
-      "Test: Pop on non-empty stack\n",
-      "Test: Pop empty stack\n",
-      "Success: test_stack_min\n"
      ]
     }
    ],
    "source": [
+    "%%writefile test_stack_min.py\n",
     "from nose.tools import assert_equal\n",
     "\n",
-    "class Test(object):\n",
+    "\n",
+    "class TestStackMin(object):\n",
     "    def test_stack_min(self):\n",
     "        print('Test: Push on empty stack, non-empty stack')\n",
     "        stack = MyStack()\n",
@@ -196,9 +204,34 @@
     "        \n",
     "        print('Success: test_stack_min')\n",
     "\n",
+    "def main():\n",
+    "    test = TestStackMin()\n",
+    "    test.test_stack_min()\n",
+    "\n",
     "if __name__ == '__main__':\n",
-    "    test = Test()\n",
+    "    main()"
-    "    test.test_stack_min()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: Push on empty stack, non-empty stack\n",
+      "Test: Pop on non-empty stack\n",
+      "Test: Pop empty stack\n",
+      "Success: test_stack_min\n"
+     ]
+    }
+   ],
+   "source": [
+    "run -i test_stack_min.py"
    ]
   }
  ],

stacks_queues/stack_min/test_stack_min.py

@@ -0,0 +1,41 @@
+from nose.tools import assert_equal
+
+
+class TestStackMin(object):
+    def test_stack_min(self):
+        print('Test: Push on empty stack, non-empty stack')
+        stack = MyStack()
+        stack.push(5)
+        assert_equal(stack.peek(), 5)
+        assert_equal(stack.min(), 5)
+        stack.push(1)
+        assert_equal(stack.peek(), 1)
+        assert_equal(stack.min(), 1)
+        stack.push(3)
+        assert_equal(stack.peek(), 3)
+        assert_equal(stack.min(), 1)
+        stack.push(0)
+        assert_equal(stack.peek(), 0)
+        assert_equal(stack.min(), 0)
+
+        print('Test: Pop on non-empty stack')
+        assert_equal(stack.pop(), 0)
+        assert_equal(stack.min(), 1)
+        assert_equal(stack.pop(), 3)
+        assert_equal(stack.min(), 1)
+        assert_equal(stack.pop(), 1)
+        assert_equal(stack.min(), 5)
+        assert_equal(stack.pop(), 5)
+        assert_equal(stack.min(), sys.maxint)
+
+        print('Test: Pop empty stack')
+        assert_equal(stack.pop(), None)
+        
+        print('Success: test_stack_min')
+
+def main():
+    test = TestStackMin()
+    test.test_stack_min()
+
+if __name__ == '__main__':
+    main()