From 8434c7d9f9cc1975160c72908e94a6be4994871f Mon Sep 17 00:00:00 2001 From: Donne Martin Date: Thu, 2 Jul 2015 23:06:09 -0400 Subject: [PATCH] Added stack min challenge. --- stacks_queues/stack_min/__init__.py | 0 .../stack_min/stack_min_challenge.ipynb | 208 ++++++++++++++++++ .../stack_min/stack_min_solution.ipynb | 57 ++++- stacks_queues/stack_min/test_stack_min.py | 41 ++++ 4 files changed, 294 insertions(+), 12 deletions(-) create mode 100644 stacks_queues/stack_min/__init__.py create mode 100644 stacks_queues/stack_min/stack_min_challenge.ipynb create mode 100644 stacks_queues/stack_min/test_stack_min.py diff --git a/stacks_queues/stack_min/__init__.py b/stacks_queues/stack_min/__init__.py new file mode 100644 index 0000000..e69de29 diff --git a/stacks_queues/stack_min/stack_min_challenge.ipynb b/stacks_queues/stack_min/stack_min_challenge.ipynb new file mode 100644 index 0000000..fbe1ee8 --- /dev/null +++ b/stacks_queues/stack_min/stack_min_challenge.ipynb @@ -0,0 +1,208 @@ +{ + "cells": [ + { + "cell_type": "markdown", + "metadata": {}, + "source": [ + "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges)." + ] + }, + { + "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 +} diff --git a/stacks_queues/stack_min/stack_min_solution.ipynb b/stacks_queues/stack_min/stack_min_solution.ipynb index cca00f5..d77b69f 100644 --- a/stacks_queues/stack_min/stack_min_solution.ipynb +++ b/stacks_queues/stack_min/stack_min_solution.ipynb @@ -4,7 +4,14 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes)." + "This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges)." + ] + }, + { + "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", - "*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.*" + "\n" ] }, { @@ -154,17 +163,16 @@ "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" + "Overwriting test_stack_min.py\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", - " test.test_stack_min()" + " main()" + ] + }, + { + "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" ] } ], diff --git a/stacks_queues/stack_min/test_stack_min.py b/stacks_queues/stack_min/test_stack_min.py new file mode 100644 index 0000000..e730921 --- /dev/null +++ b/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() \ No newline at end of file