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  1. require 'benchmark'
  2.  
  3. class TriBonacci
  4.   def initialize
  5.     @memo = [1,1,2]
  6.   end
  7.   def f(n)
  8.     return @memo[n] unless @memo[n] == nil
  9.     @memo[n] = f(n-1) + f(n-2) + f(n-3)
  10.   end
  11.   def calc(n)
  12.     last = @memo.length - 1
  13.     return @memo[n] if n <= last
  14.     (last + 1).upto(n-1) do |i|
  15.       f(i)
  16.     end
  17.     f(n)
  18.   end
  19. end
  20.  
  21. n = 6500
  22. Benchmark.bm do |x|
  23.   x.report {TriBonacci.new.f(n)}
  24.   x.report {TriBonacci.new.calc(n)}
  25. end
  26.  
  27.  
Success #stdin #stdout 0.07s 12056KB
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                 user     system      total        real
             0.020000   0.000000   0.020000 (  0.028661)
             0.020000   0.000000   0.020000 (  0.026711)
https://ideone.com/dHxqTh
language:
Ruby (ruby 2.5.5)
created:
10 years ago
visibility:
secret

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