快速排序之三青年版

/// <summary>
        /// Quick Sort
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="array"></param>
        public static void QuickSort<T>(T[] array,int left,int right) where T : IComparable
        {
            
            if (left < right)
            {
               
                int middle = GetMiddleFroQuickSort<T>(array, left, right);

                QuickSort<T>(array, left, middle - 1);

                QuickSort<T>(array, middle + 1, right);
            }
           
        }
        /// <summary>
        /// get the index of the middle value for qucik sort
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="array"></param>
        /// <param name="left"></param>
        /// <param name="right"></param>
        /// <returns></returns>
        private static int GetMiddleFroQuickSort<T>(T[] array, int left, int right) where T : IComparable
        {
            T key = array[left];
            while (left < right)
            {
                while (left < right && key.CompareTo(array[right]) < 0)
                {
                    right--;
                }
                if (left < right)
                {
                    T temp = array[left];
                    array[left] = array[right];
                    //Console.WriteLine("array[{0}]:{1} ---->  arry[{2}]:{3}", left, temp, right, array[right]);
                    left++;
                }

                while (left < right && key.CompareTo(array[left]) > 0)
                {
                    left++;
                }
                if (left < right)
                {
                    T temp = array[right];
                    array[right] = array[left];
                    //Console.WriteLine("array[{0}]:{1} ----> arry[{2}]:{3}", right, temp, left, array[left]);
                    right--;
                }
                array[left] = key;
            }
            //Console.WriteLine("find the middle value {0} and the index {1}", array[left], left);
            return left;
        }

测试代码：int[] array = new int[] {43,23,80,15,789,27,90,69,66,158,45,32,1,22,77,66,44};
            SortHelper.QuickSort<int>(array,0,array.Length-1);
            Console.WriteLine("after quick sort");
            foreach (int i in array)
            {
                Console.Write(i + "->");
            }
            Console.WriteLine();

文艺青年是这样子写的：

/// <summary>
        /// 快速排序函数
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <returns></returns>
        IEnumerable<T> QuickSorting<T>(IEnumerable<T> list) where T : IComparable<T>
        {

            if (list.Count() <= 1) return list;



            var pivot = list.First();

            return QuickSorting(list.Where(x => x.CompareTo(pivot) < 0))
                           .Concat(list.Where(x => x.CompareTo(pivot) == 0))
                           .Concat(QuickSorting(list.Where(x => x.CompareTo(pivot) > 0)));

        }

测试代码：

static void Main(string[] args)
        {
            List<int> ints = new List<int>
            {
,33,11,43,55,123,452,1,3,5,15,153,10000,532,553,22,33,11,53,11,33
            };
            List<int> lists = new Program().QuickSorting<int>(ints).ToList<int>();


            lists.ForEach(A => Console.WriteLine(A));
        }

二逼青年竟是这样子写的：

  private void checkNumOredASC(ref int[] num, int left, int right)
        {
            int i = left;
            int j = right;
            int temp;
            int middle;
            middle = num[(right + left) / 2];
            while ((num[i] < middle) && (i < right))
            {
                i++;
            }
            while ((num[j] > middle) && (j > left))
            {
                j--;
            }
            if (i <= j)
            {
                temp = num[i];
                num[i] = num[j];
                num[j] = temp;
                i++;
                j--;
            }
            if (left < j)
            {
                checkNumOredASC(ref num, left, j);
            }
            if (right > i)
            {
                checkNumOredASC(ref num, i, right);
            }
        }

测试代码：

            int[] a = new int[] {23,1,34,134,2,4,563,64,232,6,4,75,754, };

            Program p = new Program();
            p.checkNumOredASC(ref a,开头索引,结尾索引);

            foreach (var item in a)
            {
                Console.WriteLine(item);
            }