Create a balanced BST using vector in C++ STL

// C# Program for the above approach

using System;
using System.Collections.Generic;
using System.Linq;

// Node of Binary Search Tree
class Node
{
    public Node left;
    public int data;
    public Node right;

    public Node(int d)
    {
        data = d;
        left = right = null;
    }
}

class MainClass
{
    static List<int> preNode = new List<int>();
    static List<int> vec = new List<int>();

    // A function that constructs Balanced
    // Binary Search Tree from a vector
    static Node createBST(List<int> v, int start, int end)
    {
        v.Sort();

        // Base Case
        if (start > end)
            return null;

        // Get the middle element and make it root
        int mid = (start + end) / 2;
        Node root = new Node(v[mid]);

        // Recursively construct the left subtree
        // and make it left child of root
        root.left = createBST(v, start, mid - 1);

        // Recursively construct the right subtree
        // and make it right child of root
        root.right = createBST(v, mid + 1, end);

        return root;
    }

    // A utility function to print
    // preorder traversal of BST
    static List<int> preOrder(Node node)
    {
        // Root Left Right
        if (node == null)
        {
            return vec;
        }
        preNode.Add(node.data);
        preOrder(node.left);
        preOrder(node.right);
        return preNode;
    }

    // Driver Code
    public static void Main(string[] args)
    {
        List<int> v = new List<int> { 4, 3, 1, 2 };
        Node root = createBST(v, 0, v.Count - 1);

        List<int> ans = preOrder(root);
        foreach (int i in ans)
        {
            Console.Write(i + " ");
        }
    }
}

// This code is contributed by adityashatmfh