/*

Problem statement:

Binary search tree (BST) is a binary tree where the value of each node is larger or equal to the values in all the nodes in that node's left subtree and is smaller than the values in all the nodes in that node's right subtree.

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Write a function that checks if a given binary search tree contains a given value.

​

For example, for the following tree:

​

n1 (Value: 1, Left: null, Right: null)

n2 (Value: 2, Left: n1, Right: n3)

n3 (Value: 3, Left: null, Right: null)

Call to Contains(n2, 3) should return true since a tree with root at n2 contains number 3.

​

*/

​

using System;

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public class Node

{

    public int Value { get; set; }

​

    public Node Left { get; set; }

​

    public Node Right { get; set; }

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    public Node(int value, Node left, Node right)

    {

        Value = value;

        Left = left;

        Right = right;

    }

}

​

public class BinarySearchTree

{

    public static bool Contains(Node root, int value)

    {

            bool result = value==root.Value;

            if (!result)

            {

                if (value > root.Value)

                {

                    if (root.Right != null)

                    {

                        result = Contains(root.Right, value);

                    }

                }

                else

                {

                    if (root.Left != null)

                    {

                        result = Contains(root.Left, value);

                    }

                }

            }

            return result;

    }

​

    public static void Main(string[] args)

    {

        Node n1 = new Node(1, null, null);

        Node n3 = new Node(3, null, null);

        Node n2 = new Node(2, n1, n3);

​

        Console.WriteLine(Contains(n2, 3));

    }

}