find_allのindex版 - Qiita

ary = [5, 4, 1, 7, 3, 8] # 案1 p ary.each_with_index.select{|e, i| e >= 5}.map{|e| e[1]} #=>[0, 3, 5] # 案2 p ary.each_with_index.each_with_object([]){|(e, i), acc| acc << i if e >= 5} #=>[0, 3, 5] # coding: windows-31J require 'benchmark' def calc_time(comment) val = nil t = Benchmark.realtime { val = yield } puts "#{comment} #{t} (msec)" val end size = 10000000 ary = size.times.map{rand(size)} cal