euler52.ipynb

   1 {
   2  "cells": [
   3   {
   4    "cell_type": "code",
   5    "execution_count": 1,
   6    "metadata": {
   7     "collapsed": false
   8    },
   9    "outputs": [
  10     {
  11      "data": {
  12       "text/plain": [
  13        "true"
  14       ]
  15      },
  16      "execution_count": 1,
  17      "metadata": {},
  18      "output_type": "execute_result"
  19     }
  20    ],
  21    "source": [
  22     "load 'array-numbers.rb'"
  23    ]
  24   },
  25   {
  26    "cell_type": "code",
  27    "execution_count": 23,
  28    "metadata": {
  29     "collapsed": false
  30    },
  31    "outputs": [
  32     {
  33      "data": {
  34       "text/plain": [
  35        ":sequence"
  36       ]
  37      },
  38      "execution_count": 23,
  39      "metadata": {},
  40      "output_type": "execute_result"
  41     }
  42    ],
  43    "source": [
  44     "def sequence(n0=0, &generator)\n",
  45     "  Enumerator.new do |yielder|\n",
  46     "    n = n0\n",
  47     "    loop do\n",
  48     "      yielder.yield generator.call(n)\n",
  49     "      n = n + 1\n",
  50     "    end\n",
  51     "  end\n",
  52     "end"
  53    ]
  54   },
  55   {
  56    "cell_type": "code",
  57    "execution_count": 24,
  58    "metadata": {
  59     "collapsed": false
  60    },
  61    "outputs": [
  62     {
  63      "data": {
  64       "text/plain": [
  65        "[0, 2, 4, 6, 8]"
  66       ]
  67      },
  68      "execution_count": 24,
  69      "metadata": {},
  70      "output_type": "execute_result"
  71     }
  72    ],
  73    "source": [
  74     "sequence {|n| n * 2}.lazy.take(5).force"
  75    ]
  76   },
  77   {
  78    "cell_type": "code",
  79    "execution_count": 25,
  80    "metadata": {
  81     "collapsed": false
  82    },
  83    "outputs": [
  84     {
  85      "data": {
  86       "text/plain": [
  87        "[6, 8, 10, 12, 14]"
  88       ]
  89      },
  90      "execution_count": 25,
  91      "metadata": {},
  92      "output_type": "execute_result"
  93     }
  94    ],
  95    "source": [
  96     "sequence(3) {|n| n * 2}.lazy.take(5).force"
  97    ]
  98   },
  99   {
 100    "cell_type": "code",
 101    "execution_count": 19,
 102    "metadata": {
 103     "collapsed": false
 104    },
 105    "outputs": [
 106     {
 107      "data": {
 108       "text/plain": [
 109        "22"
 110       ]
 111      },
 112      "execution_count": 19,
 113      "metadata": {},
 114      "output_type": "execute_result"
 115     }
 116    ],
 117    "source": [
 118     "sequence {|n| n * 2}.lazy.select {|n| n > 20}.first"
 119    ]
 120   },
 121   {
 122    "cell_type": "code",
 123    "execution_count": 3,
 124    "metadata": {
 125     "collapsed": false
 126    },
 127    "outputs": [
 128     {
 129      "data": {
 130       "text/plain": [
 131        "[1, 2, 4, 5, 7, 8]"
 132       ]
 133      },
 134      "execution_count": 3,
 135      "metadata": {},
 136      "output_type": "execute_result"
 137     }
 138    ],
 139    "source": [
 140     "125874.to_digits.sort"
 141    ]
 142   },
 143   {
 144    "cell_type": "code",
 145    "execution_count": 4,
 146    "metadata": {
 147     "collapsed": false
 148    },
 149    "outputs": [
 150     {
 151      "data": {
 152       "text/plain": [
 153        "[1, 2, 4, 5, 7, 8]"
 154       ]
 155      },
 156      "execution_count": 4,
 157      "metadata": {},
 158      "output_type": "execute_result"
 159     }
 160    ],
 161    "source": [
 162     "(125874 * 2).to_digits.sort"
 163    ]
 164   },
 165   {
 166    "cell_type": "code",
 167    "execution_count": 9,
 168    "metadata": {
 169     "collapsed": false
 170    },
 171    "outputs": [
 172     {
 173      "data": {
 174       "text/plain": [
 175        "1"
 176       ]
 177      },
 178      "execution_count": 9,
 179      "metadata": {},
 180      "output_type": "execute_result"
 181     }
 182    ],
 183    "source": [
 184     "[125874.to_digits.sort, (125874 * 2).to_digits.sort, 124578.to_digits.sort].to_set.length"
 185    ]
 186   },
 187   {
 188    "cell_type": "code",
 189    "execution_count": 11,
 190    "metadata": {
 191     "collapsed": false
 192    },
 193    "outputs": [
 194     {
 195      "data": {
 196       "text/plain": [
 197        ":identical_multiples"
 198       ]
 199      },
 200      "execution_count": 11,
 201      "metadata": {},
 202      "output_type": "execute_result"
 203     }
 204    ],
 205    "source": [
 206     "def identical_multiples(n, max_multiplier)\n",
 207     "  (1..max_multiplier).map {|m| (n * m).to_digits.sort}.to_set.length == 1\n",
 208     "end"
 209    ]
 210   },
 211   {
 212    "cell_type": "code",
 213    "execution_count": 18,
 214    "metadata": {
 215     "collapsed": false
 216    },
 217    "outputs": [
 218     {
 219      "data": {
 220       "text/plain": [
 221        "true"
 222       ]
 223      },
 224      "execution_count": 18,
 225      "metadata": {},
 226      "output_type": "execute_result"
 227     }
 228    ],
 229    "source": [
 230     "identical_multiples(125874, 2)"
 231    ]
 232   },
 233   {
 234    "cell_type": "code",
 235    "execution_count": 26,
 236    "metadata": {
 237     "collapsed": false
 238    },
 239    "outputs": [
 240     {
 241      "data": {
 242       "text/plain": [
 243        "142857"
 244       ]
 245      },
 246      "execution_count": 26,
 247      "metadata": {},
 248      "output_type": "execute_result"
 249     }
 250    ],
 251    "source": [
 252     "sequence(1) {|n| n}.lazy.select {|n| identical_multiples n, 6}.first"
 253    ]
 254   },
 255   {
 256    "cell_type": "code",
 257    "execution_count": null,
 258    "metadata": {
 259     "collapsed": true
 260    },
 261    "outputs": [],
 262    "source": []
 263   }
 264  ],
 265  "metadata": {
 266   "kernelspec": {
 267    "display_name": "Ruby 2.4.0",
 268    "language": "ruby",
 269    "name": "ruby"
 270   },
 271   "language_info": {
 272    "file_extension": ".rb",
 273    "mimetype": "application/x-ruby",
 274    "name": "ruby",
 275    "version": "2.4.0"
 276   }
 277  },
 278  "nbformat": 4,
 279  "nbformat_minor": 0
 280 }