From 9d2655548e6cc1743fb4ab479baddc79be237640 Mon Sep 17 00:00:00 2001
From: Donne Martin <donne.martin@gmail.com>
Date: Mon, 25 May 2015 09:46:54 -0400
Subject: [PATCH] Added notebook solving the following: Implement selection
 sort.

---
 README.md                              |   4 +
 sorting-searching/selection-sort.ipynb | 147 +++++++++++++++++++++++++
 2 files changed, 151 insertions(+)
 create mode 100644 sorting-searching/selection-sort.ipynb

diff --git a/README.md b/README.md
index c3b4ebe..c68904c 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,10 @@ Continually updated IPython Notebooks containing coding problems and solutions (
 * [Implement a queue using two stacks](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/stacks-queues/queue-from-stacks.ipynb)
 * [Sort a stack using another stack as a buffer](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/stacks-queues/sort-stack.ipynb)
 
+## Sorting and Searching
+
+* [Implement selection sort](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/sorting-searching/selection-sort.ipynb#)
+
 ## Hacker Rank
 
 * [Utopian Tree](http://nbviewer.ipython.org/github/donnemartin/algorithms-data-structures/blob/master/hacker-rank/utopian-tree.ipynb)
diff --git a/sorting-searching/selection-sort.ipynb b/sorting-searching/selection-sort.ipynb
new file mode 100644
index 0000000..b512981
--- /dev/null
+++ b/sorting-searching/selection-sort.ipynb
@@ -0,0 +1,147 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Implement selection sort.\n",
+    "\n",
+    "* [Clarifying Questions](#Clarifying-Questions)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Pythonic-Code](#Pythonic-Code)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Clarifying Questions\n",
+    "\n",
+    "* Are we sorting integers?\n",
+    "    * Yes\n",
+    "* Can we assume the input is valid integers?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* Empty input\n",
+    "* One element\n",
+    "* Two or more elements"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "We can do this recursively or iteratively.  Iteratively will be more efficient as it doesn't require the extra space overhead with the recursive calls.\n",
+    "\n",
+    "* For each element\n",
+    "    * Check every element to the right to find the min\n",
+    "    * If min < current element, swap\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n^2) average, worst, best\n",
+    "* Space: O(1) iterative, O(n) recursive (unless tail-call elimination is available, then O(1))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def find_min_index(data, start):\n",
+    "    min_index = start\n",
+    "    for i in xrange(start + 1, len(data)):\n",
+    "        if data[i] < data[min_index]:\n",
+    "            min_index = i\n",
+    "    return min_index\n",
+    "\n",
+    "def swap(data, i, j):\n",
+    "    if (i != j):\n",
+    "        data[i], data[j] = data[j], data[i]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "def selection_sort_recursive(data, start):\n",
+    "    if start < len(data) - 1:\n",
+    "        swap(data, start, find_min_index(data, start))\n",
+    "        selection_sort_recursive(data, start+1)\n",
+    "\n",
+    "print('Empty input')\n",
+    "data = []\n",
+    "selection_sort_recursive(data, 0)\n",
+    "print(data)\n",
+    "print('One element')\n",
+    "data = [5]\n",
+    "selection_sort_recursive(data, 0)\n",
+    "print(data)\n",
+    "print('Two or more elements')\n",
+    "data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
+    "selection_sort_recursive(data, 0)\n",
+    "print(data)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "def selection_sort_iterative(data):\n",
+    "    if len(data) == 0 or len(data) == 1:\n",
+    "        return\n",
+    "    for i in xrange(0, len(data) - 1):\n",
+    "        swap(data, i, find_min_index(data, i))"
+   ]
+  }
+ ],
+ "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
+}