C#算法基础之快速排序

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace ConsolePractice
 {
     class CArray
     {
         private int[] arr;
         //数组大小
         private int upper;
         //下标
         private int numElements;

         /// <summary>
         /// 初始化数组参数
         /// </summary>
         /// <param name="size"></param>
         public CArray(int size)
         {
             arr = new int[size];
             upper = size - ;
             numElements = ;
         }

         /// <summary>
         /// 插入方法
         /// </summary>
         /// <param name="item">存储的数</param>
         public void Insert(int item)
         {
             arr[numElements] = item;
             numElements++;
         }

         /// <summary>
         /// 输出方法
         /// </summary>
         public void DisplayElements()
         {
             for (int i = ; i <= upper; i++)
             {
                 Console.Write(arr[i] + " ");
             }
             Console.WriteLine();
         }

         /// <summary>
         /// 清除数组
         /// </summary>
         public void Clear()
         {
             for (int i = ; i <= upper; i++)
             {
                 arr[i] = ;
             }
             numElements = ;
         }

         #region 快速排序算法
         /// <summary>
         /// 快速排序算法
         /// </summary>
         public void QSort()
         {
             RecQSort(, numElements - );
         }

         public void RecQSort(int first, int last)
         {
             if ((last - first) <= )
                 return;
             else
             {
                 int part = this.Partition(first, last);
                 RecQSort(first, part - );
                 RecQSort(part + , last);
             }
         }

         public int Partition(int first, int last)
         {
             int pivotVal = arr[first];
             int theFirst = first;
             bool okSide;
             first++;
             do
             {
                 okSide = true;
                 while (okSide)
                 {
                     if (arr[first] > pivotVal)
                         okSide = false;
                     else
                     {
                         first++;
                         okSide = (first <= last);
                     }
                 }
                 okSide = true;
                 while (okSide)
                 {
                     if (arr[last] <= pivotVal)
                         okSide = false;
                     else
                     {
                         last--;
                         okSide = (first <= last);
                     }
                 }
                 if (first < last)
                 {
                     Swap(first, last);
                     this.DisplayElements();
                     first++;
                     last--;
                 }

             } while (first <= last);
             Swap(theFirst, last);
             this.DisplayElements();
             return last;
         }

         public void Swap(int item1, int item2)
         {
             int temp = arr[item1];
             arr[item1] = arr[item2];
             arr[item2] = temp;
         }
         #endregion
     }

     class C_shape
     {
         static void Main()
         {
             CArray nums = new CArray();
             Random rnd = new Random();
             for (int i = ; i < ; i++)
             {
                 nums.Insert(rnd.Next(, ));
             }
             Console.WriteLine("Before sorting:");
             nums.DisplayElements();
             Console.WriteLine("During sorting:");
             nums.QSort();
             Console.WriteLine("After sorting:");
             nums.DisplayElements();
             Console.ReadKey();
         }
     }
 }