Question

HI i did this code with help of Marc Gravell in

Why can't I find _left and _right in BinarySearchTree?
&
How do I correct an implicit conversion error in BST C# Code?

, its Binary search tree , but now I’m having logical error the results coming are wrong the output of my code is the following:

2 3 5 6 10 17 ------------------------------------------------ 17 2 ------------------------------------------------ 3                  6 Press any key to continue . . . 

the last two number must give the total of inserted elements 6 but its showing 9

and but the way How can i get the height of the tree ?!

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using System; using System.Collections.Generic; using System.Text;  namespace errors {     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);              Console.WriteLine('------------------------------------------------');             Console.WriteLine(t.FindMax());             Console.WriteLine(t.FindMin());             Console.WriteLine('------------------------------------------------');              Console.WriteLine(t.CountLeaves(t.root));             Console.WriteLine(t.CountNodes(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.n;             }              public int FindMax()             {                 TreeNode current = root;                  while (current._right != null)                     current = current._right;                  return current.n;             }                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 int CountNodes(TreeNode root)             {                 int count=1;                 if (root._left != null)                     count += CountNodes(root._left);                 if (root._right != null)                     count += CountNodes(root._right);                 return count;             }              public int CountLeaves(TreeNode root)             {                 int count = (root._left == null && root._right == null) ? 1 : 0;                 if (root._left != null)                     count += CountLeaves(root._left);                 if (root._right != null)                     count += CountLeaves(root._right);                 return count;             }               public static void print(TreeNode root)             {                 if (root != null)                 {                     print(root._left);                     Console.WriteLine(root.n.ToString());                     print(root._right);                 }              }            }      } } 

Thanx in advance and special thanx to Marc Gravell .

Answer 1

If what you mean in CountNodes is to count all non-leaf nodes you must change this line:

int count=1; 

to read this:

int count = (root._left == null && root._right == null) ? 0 : 1; 

(the opposite of what is in CountLeaves).

And this will get you the height of the tree:

public int Height(TreeNode root) {     int height = 1;     if (root._left != null)         height = Math.Max(height, Height(root._left));     if (root._right != null)         height = Math.Max(height, Height(root._right));     return height;    }