Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

/**
 * 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;
        int leftDepth=maxDepth(root.left);
    	int rightDepth=maxDepth(root.right);
    	return (leftDepth>rightDepth?leftDepth:rightDepth)+2;
    }
}

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode *root) {
        if(root ==NULL) return 0;
        int leftDepth =maxDepth(root->left);
        int rightDepth =maxDepth(root->right);
        return (leftDepth>rightDepth?leftDepth:rightDepth)+1;
    }
};