Ruby实现的合并排序算法

算法课的作业，利用分治法，合并排序。

#encoding: utf-8
#author: xu jin, 4100213
#date: oct 27, 2012
#mergesort
#to sort an array by using mergesort algorithm
#example output:
#the original array is：[4, 32, 84, 58, 49, 40, 75, 29, 82, 21, 70, 37, 70]
#the sorted array is: [4, 21, 29, 32, 37, 40, 49, 58, 70, 70, 75, 82, 84]

max = 100
arrayint = array.new
for index in (0..12)
 arrayint[index] = rand(100) #produce 12 random number
end
puts "the original array is：" + arrayint.to_s

def merge(arr, left, middle, right)
 arrl ,arrr = array.new, array.new
 arrl[0..(middle - left)], arrr[0..(right - middle - 1)] = arr[left..middle], arr[middle + 1.. right]
 arrl[arrl.size] ,arrr[arrr.size]= max, max
 for k in (left..right)
  arrl.first <= arrr.first ? (arr[k] = arrl.shift) : (arr[k] = arrr.shift)
 end
end

def merge_sort(arr, left, right)
 if left < right then
  middle = (left + right)/2
  merge_sort(arr, left, middle)
  merge_sort(arr, middle + 1, right)
  merge(arr, left, middle, right)
 end
end

merge_sort(arrayint, 0, arrayint.length-1)
puts "the sorted array is: " + arrayint.to_s