Question

  public void HeightIterative()
    {
        int counter = 0;
        int counter2 = 0;
        TreeNode current=root;

        if(current != null)
        {
            while(current.LeftNode!=null)
            {
                counter++;
                current = current.LeftNode;
            }
            while(current.RightNode!=null)
            {
                counter2++;
                current = current.RightNode;
            }
        }

        int res = 1+Math.Max(counter, counter2);
        Console.WriteLine("The Height Of Tree Is: "+res);
    }

I wrote iterative method, to calculate height of tree. but in some cases its not working properly. As in case:
10
1
2
3
4
5
18
17
16
15
14
13
what’s the problem. according to this sequence height of tree is 6 where as my code is showing 5.

Answer 1

You are using two loops, but each loop investigated only oneside of node, but each node in tree has two sides you should investigate it all. You can do it through recursion call.

private int GetLen(TreeNode node)
{
  var result = 0;

  if(node != null)
  {
    result = Math.Max(GetLen(node.LeftNode), GetLen(node.RightNode)) + 1;
  }

  return result;
}

public void HeightIterative()
{
  int res = GetLen(root);
  Console.WriteLine("The Height Of Tree Is: "+res);
}

Iterative version:

private class NodeInfo
{
  public NodeInfo(TreeNode node, int len)
  {
    Node = node;
    Len = len;
  }

  public TreeNode Node {get; private set;}
  public int Len {get; private set;}
}

public void HeightIterative()
{
    int maxLen = 0;

    var queue = new Queue<NodeInfo>();
    queue.Enqueue(new NodeInfo(root, 1));

    while (queue.Count > 0)
    {
        var item = queue.Dequeue();
        var current = item.Node;
        var currentLen = item.Len;

        if (current.LeftNode != null)
        {
            queue.Enqueue(new NodeInfo(current.LeftNode, currentLen + 1));
        }

        if (current.RightNode != null)
        {
            queue.Enqueue(new NodeInfo(current.RightNode, currentLen + 1));
        }

        if (currentLen > maxLen)
        {
            maxLen = currentLen;
        }
    }

    Console.WriteLine("The Height Of Tree Is: " + maxLen);
}