Ruby实现的3种快速排序算法

刚学Ruby，正巧算法老师鼓励用不熟悉的语言来写算法，我就用Ruby吧~~
话说Ruby可真是超厉害，好多凭直觉的方法都可以用。。。。。无限膜拜中。。。。

期间我遇到了invalid multibyte char (US-ASCII)的错误，解决办法是在开头加一个#encoding:utf-8
这个错误在stackoverflow上有人问到过，某人给出的回答是
Write # encoding: utf-8 on top of that file. That changes the default encoding of all string/regexp literals in that file utf-8.
参考链接：http://stackoverflow.com/questions/3678172/ruby-1-9-invalid-multibyte-char-us-ascii

快速排序的普通版本：

代码如下：

#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.new

index = 0

while (index < 12)

  arrayInt[index] = rand(100)  #produce 12 random number

  index += 1

end

puts "The original array is：" + arrayInt.to_s


def QuickSort(arrayInt, first, last)

  if first < last  

    middle = Partition(arrayInt, first, last)

    QuickSort(arrayInt, first, middle - 1)

    QuickSort(arrayInt, middle + 1, last)     

  end  

end


def 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 + 1

end


QuickSort(arrayInt, 0, arrayInt.length-1)

puts "The sorted array is: " + arrayInt.to_s

快速排序的随机化版本：

代码如下：

#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.new

index = 0

while (index < 12)

  arrayInt[index] = rand(100)  #produce 12 random number

  index += 1

end

puts "The original array is：" + arrayInt.to_s


def RandomizedQuickSort(arrayInt, first, last)

  if first < last  

    middle = RandomizedPartition(arrayInt, first, last)

    RandomizedQuickSort(arrayInt, first, middle - 1)

    RandomizedQuickSort(arrayInt, middle + 1, last)     

  end  

end


def RandomizedPartition(arrayInt, first, last)

  i = rand(last - first + 1) + first 

  arrayInt[i], arrayInt[last] = arrayInt[last], arrayInt[i]

  return Partition(arrayInt, first, last)  

end


def 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 + 1

end


RandomizedQuickSort(arrayInt, 0, arrayInt.length-1)

puts "The sorted array is: " + arrayInt.to_s

快速排序的利用了Ruby的语法糖的随机化版本：

代码如下：

#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.new

index = 0

while (index < 12)

  arrayInt[index] = rand(100)  #produce 12 random number

  index += 1

end

puts "The original array is：" + arrayInt.to_s


def 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