How to count the tree levels?

Question

Hi..
I'm a new memeber here.. and I have a problem :S
My problem is about counting the maximum number of a tree levels.
the question was: write a methode that receives a root of a binary tree and returns the maximum number of levels it has.
I wrote the following methodes:
public void depth() {
System.out.print(depthHelper(root));
private int depthHelper(TreeNode node) {
int level = 1;
if (node == null) {
return 0;
level = level + depthHelper(node.rightNode);
return level;
The problem is that these methodes count levels from one side which is the right side or left side if I wrote "node.leftNode".
SO, how can I count them from both sides?
I'll be very glad if you help me.

Answer 1

It's often best to start with standard recursive tree traversal algoritm,
private dH(TreeNode node) {
   if (node != null) {
      dH(node.leftNode);
      dH(node.rightNode);
}You must keep track of the current depth and the maximum depth so far. The current depth is easy. You just increment it each time you go deeper.
private dH(TreeNode node, int current) {
   if (node != null) {
      dH(node.leftNode, current + 1);
      dH(node.rightNode, current + 1);
}The maximum depth is global to the tree so you should keep it outside the method. In each recursive step you compare it to the current depth
int maximum = 0;
private dH(TreeNode node, int current) {
   if (node != null) {
      if (current > maximum)
         maximum = current;
      dH(node.leftNode, current + 1);
      dH(node.rightNode, current + 1);
}Now maximum contains the maximum depth.