Quick sort

   class Program
    {
            public class Tree
        {
            public int data;// data 
            public Tree left;// The left subtree 
            public Tree right;// Right subtree 
            public static void Insert(Tree tree, int num)
            {
                if (tree.data <= num)
                {
                    if (tree.right != null)
                    {
                        Insert(tree.right, num);
                    }
                    else
                    {
                        Tree right = new Tree { data = num };
                        tree.right = right;
                    }
                }
                else
                {
                    if (tree.left != null)
                    {
                        Insert(tree.left, num);
                    }
                    else
                    {
                        Tree left = new Tree { data = num };
                        tree.left = left;
                    }
                }
            }
            // Tree traversal 
            public static void Travel(Tree tree)
            {
                if (tree.left != null)
                    Travel(tree.left);
                Console.Write(tree.data + "   ");
                if (tree.right != null)
                    Travel(tree.right);
            }
        }
        
            public static Tree tree;


            public static void sort(int[] a)
            {
                tree = new Tree { data = a[0] };
                for (int i = 1; i < a.Length; i++)
                {
                    Tree.Insert(tree, a[i]);
                }
            }
           
               
            
        
    
    static void Main(string[] args)
        {
            //string str= Console.ReadLine();
            //string[] array = str.Split(',');
            //List<int> intArray = new List<int>();
            //foreach (string  i in array)
            //{
            //    intArray.Add(Convert.ToInt32(i));
            //}
            int[] a = { 3, 5, 3, 6, 4, 7, 5, 7, 4, 1, 15, 8, 10, 9 };
            Console.WriteLine(" Raw data ");
            foreach (var item in a)
            {
                Console.Write(item + "   ");
            }
            Console.WriteLine();
            Console.WriteLine(" Data after sorting ");
            sort(a);
            Tree.Travel(tree);
            Console.ReadLine();

        }
        private static int DivisionLeft(List<int> list,int left,int right)
        {
            while (left<right)
            {
                int num = list[left];// Central axis 
                if(num>list[left+1]){
                    list[left] = list[left + 1];
                    list[left + 1] = num;
                    left++;
                }
                else
                {
                   
                    int temp = list[left+1];
                    list[left+1] = list[right];
                    list[right] = temp;
                    right--;
                     
                }
                
            }
            return left;
        }
        // Gets the position of the pivot after shunting left and right according to the pivot value 
        private static int Division(List<int> list, int left, int right)
        {
            while (left < right)
            {
                int num = list[left]; // Use the first element as the pivot 
                if (num > list[left + 1])
                {
                    list[left] = list[left + 1];
                    list[left + 1] = num;
                    left++;
                }
                else
                {
                    int temp = list[right];
                    list[right] = list[left + 1];
                    list[left + 1] = temp;
                    right--;
                }
                Console.WriteLine(string.Join(",", list));
            }
            Console.WriteLine("--------------\n");
            return left; // Point to the position of the pivot at this time 
        }
    }