BST C# Code with errors

Question

Hi, I wrote this code

I have these errors

Cannot implicitly convert type x.Program.TreeNode' to 'int' // on findmin

Cannot implicitly convert type x.Program.TreeNode' to 'int' // on findmax

and is my main correct or missing somethin?

and how i can count the nodes,leaves and get the hight (need only hints)

class Program
    {
        static void Main(string[] args)
        {
            BinarySearchTree t = new BinarySearchTree();

            t.insert(ref t.root, 10);
            t.insert(ref t.root, 5);
            t.insert(ref t.root, 6);
            t.insert(ref t.root, 17);
            t.insert(ref t.root, 2);
            t.insert(ref t.root, 3);

            BinarySearchTree.print(t.root);
        }

        public class TreeNode
        {
            public int n;
            public TreeNode _left;
            public TreeNode _right;


            public TreeNode(int n, TreeNode _left, TreeNode _right)
            {
                this.n = n;
                this._left = _left;
                this._right = _right;
            }


            public void DisplayNode()
            {
                Console.Write(n);
            }
        }


        public class BinarySearchTree
        {
            public TreeNode root;

            public BinarySearchTree()
            {
                root = null;
            }


            public void insert(ref TreeNode root, int x)
            {
                if (root == null)
                {
                    root = new TreeNode(x, null, null);
                }
                else
                    if (x < root.n)
                        insert(ref root._left, x);
                    else
                        insert(ref root._right, x);
            }

            public int FindMin()
            {
                TreeNode current = root;

                while (current._left != null)
                    current = current._left;

                return current;
            }

            public int FindMax()
            {
                TreeNode current = root;

                while (current._right != null)
                    current = current._right;

                return current;
            }

            public TreeNode Find(int key)
            {
                TreeNode current = root;

                while (current.n != key)
                {
                    if (key < current.n)
                        current = current._left;
                    else
                        current = current._right;
                    if (current == null)
                        return null;
                }
                return current;
            }



            public void InOrder(ref TreeNode root)
            {
                if (root != null)
                {
                    InOrder(ref root._left);
                    root.DisplayNode();
                    InOrder(ref root._right);
                }
            }


            public static void print(TreeNode root)
            {
                if (root != null)
                {
                    print(root._left);
                    Console.WriteLine(root.n.ToString());
                    print(root._right);
                }

            }

Answer 1

Since you need (FindMin/FindMax) to return an int, do you mean current.n?

---

Updated: for counting leaves and nodes, how about (as instance methods of TreeNode):

    public int CountNodes()
    {
        int count = 1; // me!
        if (_left != null) count += _left.CountNodes();
        if (_right != null) count += _right.CountNodes();
        return count;
    }

    public int CountLeaves()
    {
        int count = (_left == null && _right == null) ? 1 : 0;
        if (_left != null) count += _left.CountLeaves();
        if (_right != null) count += _right.CountLeaves();
        return count;
    }

If I've missed the point, let me know...

Answer 2

Your FindMin() and FindMax() methods are trying to return TreeNode objects but the signature says they returns ints. As it doesn't appear that the methods are used in the program, prehaps you could remove them?