Added notebook solving the following: HackerRank Utopian Tree problem.

README.md

@@ -30,7 +30,6 @@ Continually updated IPython Notebooks containing coding problems and solutions (
 * [Find the start of a linked list loop](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/linked-lists/find-loop-start.ipynb)
 * [Determine if a linked list is a palindrome](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/linked-lists/palindrome.ipynb)
 
-
 ## Stacks and Queues
 
 * [Implement a stack with push, pop, and peek methods using a linked list](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/stacks-queues/stack.ipynb)
@@ -40,6 +39,10 @@ Continually updated IPython Notebooks containing coding problems and solutions (
 * [Implement a set of stacks class that wraps a list of stacks, each bound by a capacity](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/stacks-queues/set-of-stacks.ipynb)
 * [Implement the Towers of Hanoi with 3 towers and N disks](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/stacks-queues/hanoi.ipynb)
 
+## Hacker Rank
+
+* [Utopian Tree](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/hacker-rank/utopian-tree.ipynb)
+
 ## License
 
     Copyright 2015 Donne Martin

hacker-rank/utopian-tree.ipynb

@@ -0,0 +1,91 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Utopian Tree\n",
+    "\n",
+    "From HackerRank: https://www.hackerrank.com/challenges/utopian-tree\n",
+    "\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "* If cycles is 0, return height of 1\n",
+    "* For 1 to cycles:\n",
+    "    * If cycle is odd, double height\n",
+    "    * Else, increment height\n",
+    "* Return height\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n), where n is the number of cycles, for each cycle we perform a calculation\n",
+    "* Space: O(1)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "# cycles = 0, print 1: base case\n",
+    "# cycles = 1, print 2: i = 1: 1 * 2\n",
+    "# cycles = 4, print 7: i = 1: 1 * 2, i = 2: 2 + 1, i = 3: 3 * 2, i = 4: 6 + 1\n",
+    "def calc_utopian_tree_height(cycles):\n",
+    "    height = 1\n",
+    "    if cycles == 0:\n",
+    "        return height\n",
+    "    for i in xrange(1, cycles+1):\n",
+    "        if i % 2 == 1:\n",
+    "            height *= 2\n",
+    "        else:\n",
+    "            height += 1\n",
+    "    return height\n",
+    "\n",
+    "num_lines = int(raw_input())\n",
+    "for i in range(0, num_lines):\n",
+    "    cycles = raw_input()\n",
+    "    cycles = int(cycles)\n",
+    "    res = calc_utopian_tree_height(cycles)\n",
+    "    print res"
+   ]
+  }
+ ],
+ "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": "2.7.9"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}