快速排序（C#代碼實現）

public static List<int> GetIntersection(List<int> n1,List<int> n2)
        {
            var list = new List<int>();

            QuickSort(n1, 0, n1.Count - 1);
            QuickSort(n2, 0, n2.Count - 1);

            int i = 0;
            int j = 0;
            while (i < n1.Count && j < n2.Count)
            {
                if (n1[i] == n2[j])
                {
                    list.Add(n1[i]);
                    i++;
                    j++;
                }
                else if (n1[i] < n2[j])
                {
                    i++;
                }
                else
                {
                    j++;
                }
            }

            return list;
        }
       
        public static void QuickSort(List<int> list, int begin, int end)
        {
            if( begin>=end)
            {
                return;
            }
            int index = Partitioning(list, begin, end);
            QuickSort(list,begin,index-1);
            QuickSort(list, index+1, end);
        }

        public static int Partitioning(List<int> list, int begin, int end)
        {
            int pivot = list[begin];
            int index = begin;
            while (begin < end)
            {
                while (begin < end)
                {
                    if (list[end] < pivot)
                    {                        
                        list[index] = list[end];
                        index = end;
                        begin++;
                        break;
                    }
                    end--;
                }
                
                while (begin < end)
                {
                    if (list[begin] > pivot)
                    {                        
                        list[index] = list[begin];
                        index = begin;
                        end--;
                        break;
                    }
                    begin++;
                }               
            }
            list[end] = pivot;
            return index;
        }