C# 快速排序算法演示代码

public static int[] QuickSort(int[] arr)  {      if (arr.Length <= 1)          return arr;         int pivot = arr.Length - 1;         int[] less = GetLessThanEqualToPivot(arr, pivot);      int[] greater = GetGreaterThanPivot(arr, pivot);         return Concatenate(QuickSort(less), arr[pivot], QuickSort(greater));  }     public static int[] Concatenate(int[] less, int pivotElement, int[] greater)  {      List<int> _result = new List<int>();      _result.AddRange(less);      _result.Add(pivotElement);      _result.AddRange(greater);      return _result.ToArray();  }     public static int[] GetLessThanEqualToPivot(int[] arr, int pivot)  {      List<int> _result = new List<int>();         for (int i = 0; i < arr.Length - 1; i++)      {          if (arr[i] <= arr[pivot])          {              _result.Add(arr[i]);          }      }         return _result.ToArray();  }     public static int[] GetGreaterThanPivot(int[] arr, int pivot)  {      List<int> _result = new List<int>();      for (int i = 0; i < arr.Length - 1; i++)      {          if (arr[i] > arr[pivot])          {              _result.Add(arr[i]);          }      }      return _result.ToArray();  }