added algorithms

ernestyalumni · Oct 2, 2017 · 91db157 · 91db157
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commit 91db157
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diff --git a/crack/BigO.ipynb b/crack/BigO.ipynb
diff --git a/crack/DataStruct.ipynb b/crack/DataStruct.ipynb
diff --git a/crack/Recursion.ipynb b/crack/Recursion.ipynb
@@ -0,0 +1,175 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "cf. [4.3. Calculating the Sum of a List of Numbers](http://interactivepython.org/runestone/static/pythonds/Recursion/pythondsCalculatingtheSumofaListofNumbers.html)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "25\n"
+     ]
+    }
+   ],
+   "source": [
+    "def listsum(numList):\n",
+    "    theSum = 0\n",
+    "    for i in numList:\n",
+    "        theSum = theSum + i\n",
+    "    return theSum\n",
+    "\n",
+    "print(listsum([1,3,5,7,9]))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "25\n"
+     ]
+    }
+   ],
+   "source": [
+    "def listsum(numList):\n",
+    "    if len(numList) == 1:  # base case\n",
+    "        return numList[0]\n",
+    "    else:\n",
+    "        return numList[0] + listsum(numList[1:]) # change its state and move toward base case with [1:]\n",
+    "\n",
+    "print(listsum([1,3,5,7,9]))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "[4.5. Converting an Integer to a String in Any Base](http://interactivepython.org/runestone/static/pythonds/Recursion/pythondsConvertinganIntegertoaStringinAnyBase.html)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "# base case - n < base\n",
+    "# n / base (division by the base will move us toward base case)\n",
+    "# call recursion on n/base  \n",
+    "\n",
+    "def toStr(n,base):\n",
+    "    convertString = \"0123456789ABCDEF\"\n",
+    "    if n < base:\n",
+    "        return convertString[n]\n",
+    "    else:\n",
+    "        return toStr(n // base, base) + convertString[n % base]\n",
+    "    "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "5AD\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(toStr(1453,16))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def reverseStr(s):\n",
+    "    if len(s) == 1:\n",
+    "        return s\n",
+    "    else:\n",
+    "        return reverseStr(s[1:]) + s[0]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'olleh'"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "reverseStr(\"hello\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "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": "2.7.11"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}