Given a binary tree, find its maximum depth.

    2
   / \
  1   3

    5
   / \
  3   10
 / \
1   4

Max depth in first is 1 and second is 2

This is one of the most common recursive question asked in interviews, with a simple implementation

class TreeNode {
    int val;
    TreeNode left;
 	TreeNode right;
	TreeNode(int x) { val = x; }
 }

public class MaxHeight {
  public int maxDepth(TreeNode root) {
    if (root == null)
      return 0;
    return 1+ Math.max(maxDepth(root.left) , maxDepth(root.right));
    }
}