maximum-depth-of-binary-tree

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int maxDepth(TreeNode root) {
if(root == null){
return 0;
}
else{
return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
}
}
}