euler34.ipynb

   1 {
   2  "cells": [
   3   {
   4    "cell_type": "code",
   5    "execution_count": 4,
   6    "metadata": {
   7     "collapsed": false
   8    },
   9    "outputs": [],
  10    "source": [
  11     "class Integer\n",
  12     "  def factorial\n",
  13     "    (1..self).inject(:*) || 1\n",
  14     "  end\n",
  15     "  alias :! :factorial\n",
  16     "end"
  17    ]
  18   },
  19   {
  20    "cell_type": "code",
  21    "execution_count": 11,
  22    "metadata": {
  23     "collapsed": false
  24    },
  25    "outputs": [
  26     {
  27      "data": {
  28       "text/plain": [
  29        ":to_digits"
  30       ]
  31      },
  32      "execution_count": 11,
  33      "metadata": {},
  34      "output_type": "execute_result"
  35     }
  36    ],
  37    "source": [
  38     "class Numeric\n",
  39     "  def to_digits\n",
  40     "    self.to_s.split('').map {|d| d.to_i}\n",
  41     "  end\n",
  42     "end "
  43    ]
  44   },
  45   {
  46    "cell_type": "code",
  47    "execution_count": 5,
  48    "metadata": {
  49     "collapsed": false
  50    },
  51    "outputs": [
  52     {
  53      "data": {
  54       "text/plain": [
  55        "120"
  56       ]
  57      },
  58      "execution_count": 5,
  59      "metadata": {},
  60      "output_type": "execute_result"
  61     }
  62    ],
  63    "source": [
  64     "5.factorial"
  65    ]
  66   },
  67   {
  68    "cell_type": "code",
  69    "execution_count": 6,
  70    "metadata": {
  71     "collapsed": false
  72    },
  73    "outputs": [
  74     {
  75      "data": {
  76       "text/plain": [
  77        "362880"
  78       ]
  79      },
  80      "execution_count": 6,
  81      "metadata": {},
  82      "output_type": "execute_result"
  83     }
  84    ],
  85    "source": [
  86     "9.factorial"
  87    ]
  88   },
  89   {
  90    "cell_type": "code",
  91    "execution_count": 8,
  92    "metadata": {
  93     "collapsed": false
  94    },
  95    "outputs": [
  96     {
  97      "data": {
  98       "text/plain": [
  99        "362880"
 100       ]
 101      },
 102      "execution_count": 8,
 103      "metadata": {},
 104      "output_type": "execute_result"
 105     }
 106    ],
 107    "source": [
 108     "9.!"
 109    ]
 110   },
 111   {
 112    "cell_type": "code",
 113    "execution_count": 10,
 114    "metadata": {
 115     "collapsed": false
 116    },
 117    "outputs": [
 118     {
 119      "name": "stdout",
 120      "output_type": "stream",
 121      "text": [
 122       "1, 362880, 10, false\n",
 123       "2, 725760, 100, false\n",
 124       "3, 1088640, 1000, false\n",
 125       "4, 1451520, 10000, false\n",
 126       "5, 1814400, 100000, false\n",
 127       "6, 2177280, 1000000, false\n",
 128       "7, 2540160, 10000000, true\n",
 129       "8, 2903040, 100000000, true\n",
 130       "9, 3265920, 1000000000, true\n",
 131       "10, 3628800, 10000000000, true\n"
 132      ]
 133     },
 134     {
 135      "data": {
 136       "text/plain": [
 137        "1..10"
 138       ]
 139      },
 140      "execution_count": 10,
 141      "metadata": {},
 142      "output_type": "execute_result"
 143     }
 144    ],
 145    "source": [
 146     "(1..10).each do |i|\n",
 147     "  puts \"#{i}, #{i * 9.!}, #{10 ** i}, #{i * 9.! < 10 ** i}\"\n",
 148     "end"
 149    ]
 150   },
 151   {
 152    "cell_type": "code",
 153    "execution_count": 12,
 154    "metadata": {
 155     "collapsed": false
 156    },
 157    "outputs": [
 158     {
 159      "data": {
 160       "text/plain": [
 161        "[3, 4, 5, 6, 7, 8, 9, 10]"
 162       ]
 163      },
 164      "execution_count": 12,
 165      "metadata": {},
 166      "output_type": "execute_result"
 167     }
 168    ],
 169    "source": [
 170     "(3..10).to_a"
 171    ]
 172   },
 173   {
 174    "cell_type": "code",
 175    "execution_count": 13,
 176    "metadata": {
 177     "collapsed": false
 178    },
 179    "outputs": [
 180     {
 181      "data": {
 182       "text/plain": [
 183        ":factorial_sum?"
 184       ]
 185      },
 186      "execution_count": 13,
 187      "metadata": {},
 188      "output_type": "execute_result"
 189     }
 190    ],
 191    "source": [
 192     "def factorial_sum?(n)\n",
 193     "  n.to_digits.map {|d| d.!}.reduce(:+) == n\n",
 194     "end"
 195    ]
 196   },
 197   {
 198    "cell_type": "code",
 199    "execution_count": 14,
 200    "metadata": {
 201     "collapsed": false
 202    },
 203    "outputs": [
 204     {
 205      "data": {
 206       "text/plain": [
 207        "145"
 208       ]
 209      },
 210      "execution_count": 14,
 211      "metadata": {},
 212      "output_type": "execute_result"
 213     }
 214    ],
 215    "source": [
 216     "145.to_digits.map {|d| d.!}.reduce(:+)"
 217    ]
 218   },
 219   {
 220    "cell_type": "code",
 221    "execution_count": 15,
 222    "metadata": {
 223     "collapsed": false
 224    },
 225    "outputs": [
 226     {
 227      "data": {
 228       "text/plain": [
 229        "745"
 230       ]
 231      },
 232      "execution_count": 15,
 233      "metadata": {},
 234      "output_type": "execute_result"
 235     }
 236    ],
 237    "source": [
 238     "146.to_digits.map {|d| d.!}.reduce(:+)"
 239    ]
 240   },
 241   {
 242    "cell_type": "code",
 243    "execution_count": 16,
 244    "metadata": {
 245     "collapsed": false
 246    },
 247    "outputs": [
 248     {
 249      "data": {
 250       "text/plain": [
 251        "120"
 252       ]
 253      },
 254      "execution_count": 16,
 255      "metadata": {},
 256      "output_type": "execute_result"
 257     }
 258    ],
 259    "source": [
 260     "5.!"
 261    ]
 262   },
 263   {
 264    "cell_type": "code",
 265    "execution_count": 17,
 266    "metadata": {
 267     "collapsed": false
 268    },
 269    "outputs": [
 270     {
 271      "data": {
 272       "text/plain": [
 273        "720"
 274       ]
 275      },
 276      "execution_count": 17,
 277      "metadata": {},
 278      "output_type": "execute_result"
 279     }
 280    ],
 281    "source": [
 282     "6.!"
 283    ]
 284   },
 285   {
 286    "cell_type": "code",
 287    "execution_count": 18,
 288    "metadata": {
 289     "collapsed": false
 290    },
 291    "outputs": [
 292     {
 293      "data": {
 294       "text/plain": [
 295        "[145]"
 296       ]
 297      },
 298      "execution_count": 18,
 299      "metadata": {},
 300      "output_type": "execute_result"
 301     }
 302    ],
 303    "source": [
 304     "(3..1000).select {|n| factorial_sum? n}.to_a"
 305    ]
 306   },
 307   {
 308    "cell_type": "code",
 309    "execution_count": 19,
 310    "metadata": {
 311     "collapsed": false
 312    },
 313    "outputs": [
 314     {
 315      "data": {
 316       "text/plain": [
 317        "[145, 40585]"
 318       ]
 319      },
 320      "execution_count": 19,
 321      "metadata": {},
 322      "output_type": "execute_result"
 323     }
 324    ],
 325    "source": [
 326     "(3..10**7).select {|n| factorial_sum? n}.to_a"
 327    ]
 328   },
 329   {
 330    "cell_type": "code",
 331    "execution_count": 20,
 332    "metadata": {
 333     "collapsed": false
 334    },
 335    "outputs": [
 336     {
 337      "data": {
 338       "text/plain": [
 339        "40730"
 340       ]
 341      },
 342      "execution_count": 20,
 343      "metadata": {},
 344      "output_type": "execute_result"
 345     }
 346    ],
 347    "source": [
 348     "(3..10**7).select {|n| factorial_sum? n}.sum"
 349    ]
 350   },
 351   {
 352    "cell_type": "code",
 353    "execution_count": null,
 354    "metadata": {
 355     "collapsed": true
 356    },
 357    "outputs": [],
 358    "source": []
 359   }
 360  ],
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 362   "kernelspec": {
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 364    "language": "ruby",
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 376 }