leetcode 2, maximum depth of binary tree

 * 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 (TreeNode *root) {
        if (root != NULL) {
            int imaxDepth = 1;
            int leftDepth = maxDepth(root->left);
            int rightDepth = maxDepth(root->right);
            imaxDepth = imaxDepth + (leftDepth > rightDepth ? leftDepth : rightDepth);
            return imaxDepth;
        }
        return 0;
    }
};