{ "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: Check if a binary tree is balanced.\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", "* Is a balanced tree one where the heights of two sub trees of any node doesn't differ by more than 1?\n", " * Yes\n", "* If this is called on a None input, should we raise an exception?\n", " * Yes\n", "* Can we assume we already have a Node class with an insert method?\n", " * Yes\n", "* Can we assume this fits memory?\n", " * Yes" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Test Cases\n", "\n", "* None -> No\n", "* 1 -> Yes\n", "* 5, 3, 8, 1, 4 -> Yes\n", "* 5, 3, 8, 9, 10 -> No" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Algorithm\n", "\n", "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_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 ../bst/bst.py\n", "%load ../bst/bst.py" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false }, "outputs": [], "source": [ "class BstBalance(Bst):\n", "\n", " def check_balance(self):\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_check_balance.py\n", "from nose.tools import assert_equal\n", "from nose.tools import raises\n", "\n", "\n", "class TestCheckBalance(object):\n", "\n", " @raises(Exception)\n", " def test_check_balance_empty(self):\n", " bst = BstBalance(None)\n", " bst.check_balance()\n", "\n", " def test_check_balance(self):\n", " bst = BstBalance(Node(5))\n", " assert_equal(bst.check_balance(), True)\n", "\n", " bst.insert(3)\n", " bst.insert(8)\n", " bst.insert(1)\n", " bst.insert(4)\n", " assert_equal(bst.check_balance(), True)\n", "\n", " bst = BstBalance(Node(5))\n", " bst.insert(3)\n", " bst.insert(8)\n", " bst.insert(9)\n", " bst.insert(10)\n", " assert_equal(bst.check_balance(), False)\n", "\n", " bst = BstBalance(Node(3))\n", " bst.insert(2)\n", " bst.insert(1)\n", " bst.insert(5)\n", " bst.insert(4)\n", " bst.insert(6)\n", " bst.insert(7)\n", " assert_equal(bst.check_balance(), True)\n", "\n", " print('Success: test_check_balance')\n", "\n", "\n", "def main():\n", " test = TestCheckBalance()\n", " test.test_check_balance_empty()\n", " test.test_check_balance()\n", "\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/interactive-coding-challenges/blob/master/graphs_trees/check_balance/check_balance_solution.ipynb) for a discussion on algorithms and code solutions." ] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.5.0" } }, "nbformat": 4, "nbformat_minor": 0 }