binary_search and find_index

sort.rb

require 'benchmark'
def binary_search(arr,element)
  l = 0
  r = arr.length - 1

  while l <= r

    mid = l + ((r-l)/2)
    if  arr[mid] == element
      return mid
    elsif arr[mid] > element
      r = mid - 1
    else
      l = mid + 1
    end
  end

  return "找不到对应的元素"
end

def sorted_array(length)
  arr = Array.new(length) { rand(10000) }
  arr.sort
end

a1 = sorted_array 10
a2 = sorted_array 10_000
a3 = sorted_array 1_000_000

Benchmark.bm do |x|
  x.report("10个元素的运行效果"){binary_search(a1,351)}
  x.report("10000个元素的运行效果"){binary_search(a2,351)}
  x.report("1000000个元素的运行效果"){binary_search(a3,351)}
end