Self-describing numbers: Difference between revisions
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m (→{{header|Sidef}}: improved the example and added a closed-form solution) |
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<lang ruby>func sdn(n) { |
<lang ruby>func sdn(n) { |
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var b = [0]*n.len; |
var b = [0]*n.len; |
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var a = n. |
var a = n.chars; |
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a.each { |i| b[i] := 0 ++ } |
a.each { |i| b[i] := 0 ++ } |
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a.join == b.join; |
a.join == b.join; |
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} |
} |
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var values = |
var values = <1210 2020 21200 3211000 |
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42101000 521001000 6210001000 27 115508 |
42101000 521001000 6210001000 27 115508>; |
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values.each { |test| |
values.each { |test| |
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} |
} |
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say "\nSelf-descriptive number less than 1e5 (in base 10):" |
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0.to(1e5).each { |i| say i if sdn(i.to_s) }</lang> |
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{{out}} |
{{out}} |
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<pre> |
<pre> |
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27 is NOT a self describing number. |
27 is NOT a self describing number. |
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115508 is NOT a self describing number. |
115508 is NOT a self describing number. |
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Self-descriptive number less than 1e5 (in base 10): |
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1210 |
1210 |
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2020 |
2020 |
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21200 |
21200 |
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</pre> |
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^C |
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'''Extra credit:''' this will generate all the self-describing numbers in bases 7 to 36: |
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<lang ruby>7.to(36).each { |b| |
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var n = ((b-4) * b**(b-1) + 2*(b**(b-2)) + b**(b-3) + b**3 -> base(b)); |
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say "base #{'%2d' % b}: #{n}"; |
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}</lang> |
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{{out}} |
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<pre> |
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base 7: 3211000 |
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base 8: 42101000 |
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base 9: 521001000 |
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base 10: 6210001000 |
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base 11: 72100001000 |
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base 12: 821000001000 |
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base 13: 9210000001000 |
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base 14: a2100000001000 |
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base 15: b21000000001000 |
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base 16: c210000000001000 |
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base 17: d2100000000001000 |
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base 18: e21000000000001000 |
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base 19: f210000000000001000 |
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base 20: g2100000000000001000 |
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base 21: h21000000000000001000 |
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base 22: i210000000000000001000 |
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base 23: j2100000000000000001000 |
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base 24: k21000000000000000001000 |
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base 25: l210000000000000000001000 |
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base 26: m2100000000000000000001000 |
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base 27: n21000000000000000000001000 |
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base 28: o210000000000000000000001000 |
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base 29: p2100000000000000000000001000 |
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base 30: q21000000000000000000000001000 |
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base 31: r210000000000000000000000001000 |
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base 32: s2100000000000000000000000001000 |
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base 33: t21000000000000000000000000001000 |
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base 34: u210000000000000000000000000001000 |
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base 35: v2100000000000000000000000000001000 |
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base 36: w21000000000000000000000000000001000 |
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</pre> |
</pre> |
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