快速排序（Ruby）

剛學Ruby，正巧演算法老師鼓勵用不熟悉的語言來寫演算法，我就用Ruby吧~~

話說Ruby可真是超厲害，好多憑直覺的方法都可以用。。。。。無限膜拜中。。。。

期間我遇到了invalid multibyte char (US-ASCII)的錯誤，解決辦法是在開頭加一個#encoding:utf-8

這個錯誤在stackoverflow上有人問到過，某人給出的回答是

Write # encoding: utf-8 on
top of that file. That changes the default encoding of all string/regexp literals in that file utf-8.

參考連結：http://stackoverflow.com/questions/3678172/ruby-1-9-invalid-multibyte-char-us-ascii

參考資料：演算法導論，github.com/kanwei

快速排序的普通版本：

#encoding: utf-8#author: xu jin, 4100213#date: Oct 20, 2012#RandomizedQuickSort#to sort an array by using QuickSort#example:#The original array is：[10, 35, 25, 67, 69, 52, 24, 40, 69, 76, 6, 49]#The sorted array is: [6, 10, 24, 25, 35, 40, 49, 52, 67, 69, 69, 76]arrayInt = Array.newindex = 0while (index < 12)  arrayInt[index] = rand(100)  #produce 12 random number  index += 1endputs "The original array is：" + arrayInt.to_sdef QuickSort(arrayInt, first, last)  if first < last      middle = Partition(arrayInt, first, last)    QuickSort(arrayInt, first, middle - 1)    QuickSort(arrayInt, middle + 1, last)       end  enddef Partition(arrayInt, first, last)    x = arrayInt[last]  i = first - 1  for j in first .. (last - 1)    if arrayInt[j] <= x        i += 1       arrayInt[i], arrayInt[j] = arrayInt[j], arrayInt[i]  #exchange    end  end  arrayInt[i + 1], arrayInt[last] = arrayInt[last], arrayInt[i + 1]  return i + 1endQuickSort(arrayInt, 0, arrayInt.length-1)puts "The sorted array is: " + arrayInt.to_s

快速排序的隨機化版本：

#encoding: utf-8#author: xu jin, 4100213#date: Oct 20, 2012#RandomizedQuickSort#to sort an array by using randomized QuickSort#example: #The original array is：[14, 47, 46, 49, 82, 76, 92, 22, 44, 81, 59, 61]#The sorted array is: [14, 22, 44, 46, 47, 49, 59, 61, 76, 81, 82, 92]arrayInt = Array.newindex = 0while (index < 12)  arrayInt[index] = rand(100)  #produce 12 random number  index += 1endputs "The original array is：" + arrayInt.to_sdef RandomizedQuickSort(arrayInt, first, last)  if first < last      middle = RandomizedPartition(arrayInt, first, last)    RandomizedQuickSort(arrayInt, first, middle - 1)    RandomizedQuickSort(arrayInt, middle + 1, last)       end  enddef RandomizedPartition(arrayInt, first, last)  i = rand(last - first + 1) + first   arrayInt[i], arrayInt[last] = arrayInt[last], arrayInt[i]  return Partition(arrayInt, first, last)  enddef Partition(arrayInt, first, last)    x = arrayInt[last]  i = first - 1  for j in first .. (last - 1)    if arrayInt[j] <= x        i += 1       arrayInt[i], arrayInt[j] = arrayInt[j], arrayInt[i]  #exchange    end  end  arrayInt[i + 1], arrayInt[last] = arrayInt[last], arrayInt[i + 1]  return i + 1endRandomizedQuickSort(arrayInt, 0, arrayInt.length-1)puts "The sorted array is: " + arrayInt.to_s

快速排序的利用了Ruby的文法糖的隨機化版本：

#encoding: utf-8#author: xu jin, 4100213#date: Oct 20, 2012#RandomizedQuickSort#to sort an array by using randomized QuickSort#example: #The original array is：[14, 47, 46, 49, 82, 76, 92, 22, 44, 81, 59, 61]#The sorted array is: [14, 22, 44, 46, 47, 49, 59, 61, 76, 81, 82, 92]arrayInt = Array.newindex = 0while (index < 12)  arrayInt[index] = rand(100)  #produce 12 random number  index += 1endputs "The original array is：" + arrayInt.to_sdef RandomizedQuickSort(a)   i = rand(a.length)  a[i], a[a.length - 1] = a[a.length - 1], a[i]  (x=a.pop) ? RandomizedQuickSort(a.select{|i| i <= x}) + [x] + RandomizedQuickSort(a.select{|i| i > x}) : []  end puts "The sorted array is: " + RandomizedQuickSort(arrayInt).to_s