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https://github.com/TheAlgorithms/Ruby
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32 lines
639 B
Ruby
32 lines
639 B
Ruby
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# A ruby program for Lucas series
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#
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# The Lucas numbers, commonly denoted L(n) form a sequence,
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# called the Lucas series, such that each number is the sum
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# of the two preceding ones, starting from 2 and 1. That is,
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#
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# L(0) = 2, L(1) = 1
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# L(n) = L(n - 1) + L(n - 2), for n > 1.
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#
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# Given n, calculate L(n).
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# Example: 2 1 3 4 7 11 18...
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# Resource: https://en.wikipedia.org/wiki/Lucas_number
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def lucas(number)
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golden_ratio = (1 + 5**0.5) / 2
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((golden_ratio**number).round()).to_i
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rescue
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"Error: Provide number only!"
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end
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puts lucas(4)
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# 7
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puts lucas(3)
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# 4
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puts lucas("3")
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# Error: Provide number only!
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puts lucas(2)
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# 3
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