鸡尾酒排序

类别：排序-交换排序
参看 维基百科的定义

鸡尾酒排序，也就是定向冒泡排序, 鸡尾酒搅拌排序, 搅拌排序 (也可以视作选择排序的一种变形), 涟漪排序, 来回排序 or 快乐小时排序, 是冒泡排序的一种变形。此算法与冒泡排序的不同处在于排序时是以双向在序列中进行排序。

using System;
 using System.Collections.Generic;

namespace Com.Colobu.Algorithm.Exchange
{
    /// <summary>
    /// <b>鸡尾酒排序</b>，也就是双向冒泡排序(bidirectional bubble sort), 鸡尾酒搅拌排序, 搅拌排序 
    /// (也可以视作选择排序的一种变形), 涟漪排序, 来回排序 or 快乐小时排序, 
    /// 是冒泡排序的一种变形。
    /// 此算法与冒泡排序的不同处在于排序时是以双向在序列中进行排序。
    /// 
    /// 平均时间复杂度:O(n^2)
    /// Stability:Yes
    /// </summary>
    public class CocktailSortAlgorithm
    {
        public static void CocktailSort<T>(IList<T> szArray) where T : IComparable
        {
            int bottom = 0;
            int top = szArray.Count - 1;
            bool swapped = true;
            while (swapped == true) // if no elements have been swapped, then the list is sorted
            {
                swapped = false;
                for (int i = bottom; i < top; i = i + 1)
                {
                    if (szArray[i].CompareTo(szArray[i + 1]) > 0)  // test whether the two elements are in the correct order
                    {
                        Swap(szArray,i,i + 1); // let the two elements change places
                        swapped = true;
                    }
                }
                // decreases top the because the element with the largest value in the unsorted
                // part of the list is now on the position top 
                top = top - 1;
                for (int i = top; i > bottom; i = i - 1)
                {
                    if (szArray[i].CompareTo(szArray[i - 1]) < 0)
                    {
                        Swap(szArray,i,i - 1);
                        swapped = true;
                    }
                }
                // increases bottom because the element with the smallest value in the unsorted 
                // part of the list is now on the position bottom 
                bottom = bottom + 1;
            }
        }

        private static void Swap<T>(IList<T> szArray, int i,int j)
        {
            T tmp = szArray[i];
            szArray[i] = szArray[j];
            szArray[j] = tmp;
        }
    }
}