40 lines
910 B
Ruby
40 lines
910 B
Ruby
# Recursive
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def factorial_recursive(n)
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n.zero? ? 1 : n * factorial_recursive(n - 1)
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end
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# Tail-recursive
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def factorial_tail_recursive(n, prod = 1)
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n.zero? ? prod : factorial_tail_recursive(n - 1, prod * n)
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end
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# Iterative with Range#each
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def factorial_iterative(n)
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(2 .. n - 1).each {|i| n *= i}
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n
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end
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# Iterative with Range#inject
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def factorial_inject(n)
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(1..n).inject {|prod, i| prod * i}
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end
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# Iterative with Range#reduce, requires Ruby 1.8.7
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def factorial_reduce(n)
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(2..n).reduce(1, :*)
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end
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require 'benchmark'
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n = 400
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m = 10000
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Benchmark.bm(16) do |b|
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b.report('recursive:') {m.times {factorial_recursive(n)}}
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b.report('tail recursive:') {m.times {factorial_tail_recursive(n)}}
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b.report('iterative:') {m.times {factorial_iterative(n)}}
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b.report('inject:') {m.times {factorial_inject(n)}}
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b.report('reduce:') {m.times {factorial_reduce(n)}}
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end
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