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| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "## Recursion\n", |
| 8 | + "A function making one or more call to itself.\n", |
| 9 | + "A simple example is demonstrated by writing a factorial function." |
| 10 | + ] |
| 11 | + }, |
| 12 | + { |
| 13 | + "cell_type": "code", |
| 14 | + "execution_count": 4, |
| 15 | + "metadata": {}, |
| 16 | + "outputs": [ |
| 17 | + { |
| 18 | + "data": { |
| 19 | + "text/plain": [ |
| 20 | + "24" |
| 21 | + ] |
| 22 | + }, |
| 23 | + "execution_count": 4, |
| 24 | + "metadata": {}, |
| 25 | + "output_type": "execute_result" |
| 26 | + } |
| 27 | + ], |
| 28 | + "source": [ |
| 29 | + "def factorial(n):\n", |
| 30 | + " if n == 0:\n", |
| 31 | + " return 1\n", |
| 32 | + " if n == 1:\n", |
| 33 | + " return 1\n", |
| 34 | + " a=n*factorial(n-1)\n", |
| 35 | + " return a\n", |
| 36 | + "factorial(4)" |
| 37 | + ] |
| 38 | + }, |
| 39 | + { |
| 40 | + "cell_type": "code", |
| 41 | + "execution_count": 6, |
| 42 | + "metadata": {}, |
| 43 | + "outputs": [ |
| 44 | + { |
| 45 | + "data": { |
| 46 | + "text/plain": [ |
| 47 | + "10" |
| 48 | + ] |
| 49 | + }, |
| 50 | + "execution_count": 6, |
| 51 | + "metadata": {}, |
| 52 | + "output_type": "execute_result" |
| 53 | + } |
| 54 | + ], |
| 55 | + "source": [ |
| 56 | + "\"\"\"\n", |
| 57 | + "sum from 0 to n, given n is an integer\n", |
| 58 | + "\"\"\"\n", |
| 59 | + "\n", |
| 60 | + "def sum_integer(n):\n", |
| 61 | + " if n == 0:\n", |
| 62 | + " return 0\n", |
| 63 | + " s = n + sum_integer(n-1)\n", |
| 64 | + " return s\n", |
| 65 | + "sum_integer(4)" |
| 66 | + ] |
| 67 | + }, |
| 68 | + { |
| 69 | + "cell_type": "code", |
| 70 | + "execution_count": 13, |
| 71 | + "metadata": {}, |
| 72 | + "outputs": [ |
| 73 | + { |
| 74 | + "data": { |
| 75 | + "text/plain": [ |
| 76 | + "26" |
| 77 | + ] |
| 78 | + }, |
| 79 | + "execution_count": 13, |
| 80 | + "metadata": {}, |
| 81 | + "output_type": "execute_result" |
| 82 | + } |
| 83 | + ], |
| 84 | + "source": [ |
| 85 | + "\"\"\"\n", |
| 86 | + "Given a number, return the sum of integers\n", |
| 87 | + "\"\"\"\n", |
| 88 | + "\n", |
| 89 | + "def sum_of_digits(n):\n", |
| 90 | + " if n%10 == 0:\n", |
| 91 | + " return 0\n", |
| 92 | + " s= (n%10) + sum_of_digits(n//10)\n", |
| 93 | + " return s\n", |
| 94 | + "\n", |
| 95 | + "sum_of_digits(7865)" |
| 96 | + ] |
| 97 | + }, |
| 98 | + { |
| 99 | + "cell_type": "code", |
| 100 | + "execution_count": 16, |
| 101 | + "metadata": {}, |
| 102 | + "outputs": [ |
| 103 | + { |
| 104 | + "data": { |
| 105 | + "text/plain": [ |
| 106 | + "['the', 'man', 'ran']" |
| 107 | + ] |
| 108 | + }, |
| 109 | + "execution_count": 16, |
| 110 | + "metadata": {}, |
| 111 | + "output_type": "execute_result" |
| 112 | + } |
| 113 | + ], |
| 114 | + "source": [ |
| 115 | + "\"\"\"\n", |
| 116 | + "Given a string phrase and a set of list words. Split string such that words from the list are made\n", |
| 117 | + "\"\"\"\n", |
| 118 | + "def word_split(phrase, l_words, output = None):\n", |
| 119 | + " if output is None:\n", |
| 120 | + " output = []\n", |
| 121 | + " for word in l_words:\n", |
| 122 | + " if phrase.startswith(word):\n", |
| 123 | + " output.append(word)\n", |
| 124 | + " return word_split(phrase[len(word):], l_words, output)\n", |
| 125 | + " return output\n", |
| 126 | + "word_split('themanran',['the', 'ran', 'man'])" |
| 127 | + ] |
| 128 | + }, |
| 129 | + { |
| 130 | + "cell_type": "markdown", |
| 131 | + "metadata": {}, |
| 132 | + "source": [ |
| 133 | + "## Memoization\n", |
| 134 | + "\n", |
| 135 | + "## Interview Questions" |
| 136 | + ] |
| 137 | + }, |
| 138 | + { |
| 139 | + "cell_type": "code", |
| 140 | + "execution_count": 23, |
| 141 | + "metadata": {}, |
| 142 | + "outputs": [ |
| 143 | + { |
| 144 | + "data": { |
| 145 | + "text/plain": [ |
| 146 | + "'kjhgfdcba'" |
| 147 | + ] |
| 148 | + }, |
| 149 | + "execution_count": 23, |
| 150 | + "metadata": {}, |
| 151 | + "output_type": "execute_result" |
| 152 | + } |
| 153 | + ], |
| 154 | + "source": [ |
| 155 | + "\"\"\"\n", |
| 156 | + "Reverse a string using recursion\n", |
| 157 | + "\"\"\"\n", |
| 158 | + "def reverse(s):\n", |
| 159 | + " if len(s) == 1:\n", |
| 160 | + " return s\n", |
| 161 | + " return reverse(s[1:]) + s[0]\n", |
| 162 | + "reverse(\"abcdfghjk\")" |
| 163 | + ] |
| 164 | + }, |
| 165 | + { |
| 166 | + "cell_type": "code", |
| 167 | + "execution_count": 24, |
| 168 | + "metadata": {}, |
| 169 | + "outputs": [], |
| 170 | + "source": [ |
| 171 | + "\"\"\"\n", |
| 172 | + "Find all permutations of a given string. If character is repeating, treat each as distinct\n", |
| 173 | + "If not using recursion, you can use itertools library\n", |
| 174 | + "\"\"\"\n", |
| 175 | + "def permutation(s):\n", |
| 176 | + " out = []\n", |
| 177 | + " if len(s) == 1:\n", |
| 178 | + " out = [s]\n", |
| 179 | + " else:\n", |
| 180 | + " for i,let in enumerate(s):\n", |
| 181 | + " for perm in permute(s[:i] + s[i+1:]):\n", |
| 182 | + " out += [let+perm]\n", |
| 183 | + " return out\n", |
| 184 | + "per " |
| 185 | + ] |
| 186 | + }, |
| 187 | + { |
| 188 | + "cell_type": "code", |
| 189 | + "execution_count": null, |
| 190 | + "metadata": {}, |
| 191 | + "outputs": [], |
| 192 | + "source": [] |
| 193 | + } |
| 194 | + ], |
| 195 | + "metadata": { |
| 196 | + "kernelspec": { |
| 197 | + "display_name": "Python 3", |
| 198 | + "language": "python", |
| 199 | + "name": "python3" |
| 200 | + }, |
| 201 | + "language_info": { |
| 202 | + "codemirror_mode": { |
| 203 | + "name": "ipython", |
| 204 | + "version": 3 |
| 205 | + }, |
| 206 | + "file_extension": ".py", |
| 207 | + "mimetype": "text/x-python", |
| 208 | + "name": "python", |
| 209 | + "nbconvert_exporter": "python", |
| 210 | + "pygments_lexer": "ipython3", |
| 211 | + "version": "3.7.3" |
| 212 | + } |
| 213 | + }, |
| 214 | + "nbformat": 4, |
| 215 | + "nbformat_minor": 2 |
| 216 | +} |
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