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();}