euler49.ipynb

   1 {
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   3   {
   4    "cell_type": "code",
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  10     {
  11      "data": {
  12       "text/plain": [
  13        "true"
  14       ]
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  16      "execution_count": 1,
  17      "metadata": {},
  18      "output_type": "execute_result"
  19     }
  20    ],
  21    "source": [
  22     "load 'primes.rb'\n",
  23     "load 'array-numbers.rb'"
  24    ]
  25   },
  26   {
  27    "cell_type": "code",
  28    "execution_count": 13,
  29    "metadata": {
  30     "collapsed": false
  31    },
  32    "outputs": [
  33     {
  34      "data": {
  35       "text/plain": [
  36        "[1, 2, 3, 4]"
  37       ]
  38      },
  39      "execution_count": 13,
  40      "metadata": {},
  41      "output_type": "execute_result"
  42     }
  43    ],
  44    "source": [
  45     "1234.to_digits"
  46    ]
  47   },
  48   {
  49    "cell_type": "code",
  50    "execution_count": 53,
  51    "metadata": {
  52     "collapsed": false
  53    },
  54    "outputs": [
  55     {
  56      "data": {
  57       "text/plain": [
  58        ":valid"
  59       ]
  60      },
  61      "execution_count": 53,
  62      "metadata": {},
  63      "output_type": "execute_result"
  64     }
  65    ],
  66    "source": [
  67     "def valid(n, debug=false)\n",
  68     "  digits = n.to_digits\n",
  69     "  perms = digits.permutation.select {|ds| ds.to_i.prime?}.to_set.to_a.permutation(3)\n",
  70     "  puts \"perms: #{perms}\" if debug\n",
  71     "  triples = perms.to_a.map {|t| t.map {|ds| ds.to_i}}\n",
  72     "  puts \"triples: #{triples}\" if debug\n",
  73     "  valids = triples.select {|t| t[0] == n && t[1] > t[0] && t[1] - t[0] == t[2] - t[1]}\n",
  74     "  puts \"valids: #{valids}\" if debug\n",
  75     "  valids[0]\n",
  76     "end"
  77    ]
  78   },
  79   {
  80    "cell_type": "code",
  81    "execution_count": 35,
  82    "metadata": {
  83     "collapsed": false
  84    },
  85    "outputs": [
  86     {
  87      "data": {
  88       "text/plain": [
  89        "false"
  90       ]
  91      },
  92      "execution_count": 35,
  93      "metadata": {},
  94      "output_type": "execute_result"
  95     }
  96    ],
  97    "source": [
  98     "valid(1234)"
  99    ]
 100   },
 101   {
 102    "cell_type": "code",
 103    "execution_count": 56,
 104    "metadata": {
 105     "collapsed": false
 106    },
 107    "outputs": [
 108     {
 109      "data": {
 110       "text/plain": [
 111        "[148748178147, 296962999629]"
 112       ]
 113      },
 114      "execution_count": 56,
 115      "metadata": {},
 116      "output_type": "execute_result"
 117     }
 118    ],
 119    "source": [
 120     "(1000..9999).map {|n| valid n}.select {|t| !t.nil?}.map {|t| t.flat_map {|n| n.to_digits}.to_i}"
 121    ]
 122   },
 123   {
 124    "cell_type": "code",
 125    "execution_count": 57,
 126    "metadata": {
 127     "collapsed": false,
 128     "scrolled": true
 129    },
 130    "outputs": [
 131     {
 132      "name": "stdout",
 133      "output_type": "stream",
 134      "text": [
 135       "perms: #<Enumerator:0x005594b994f0e0>\n",
 136       "triples: [[2969, 2699, 9629], [2969, 2699, 6299], [2969, 9629, 2699], [2969, 9629, 6299], [2969, 6299, 2699], [2969, 6299, 9629], [2699, 2969, 9629], [2699, 2969, 6299], [2699, 9629, 2969], [2699, 9629, 6299], [2699, 6299, 2969], [2699, 6299, 9629], [9629, 2969, 2699], [9629, 2969, 6299], [9629, 2699, 2969], [9629, 2699, 6299], [9629, 6299, 2969], [9629, 6299, 2699], [6299, 2969, 2699], [6299, 2969, 9629], [6299, 2699, 2969], [6299, 2699, 9629], [6299, 9629, 2969], [6299, 9629, 2699]]\n",
 137       "valids: [[2969, 6299, 9629]]\n"
 138      ]
 139     },
 140     {
 141      "data": {
 142       "text/plain": [
 143        "[2969, 6299, 9629]"
 144       ]
 145      },
 146      "execution_count": 57,
 147      "metadata": {},
 148      "output_type": "execute_result"
 149     }
 150    ],
 151    "source": [
 152     "valid(2969, debug=true)"
 153    ]
 154   },
 155   {
 156    "cell_type": "code",
 157    "execution_count": null,
 158    "metadata": {
 159     "collapsed": true
 160    },
 161    "outputs": [],
 162    "source": []
 163   }
 164  ],
 165  "metadata": {
 166   "kernelspec": {
 167    "display_name": "Ruby 2.4.0",
 168    "language": "ruby",
 169    "name": "ruby"
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 172    "file_extension": ".rb",
 173    "mimetype": "application/x-ruby",
 174    "name": "ruby",
 175    "version": "2.4.0"
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 180 }