maximum-depth-of-binary-tree

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
 * 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 (NULL == root)
        return 0;
    int le = maxDepth(root->left);
    int ri = maxDepth(root->right);

    return le > ri ? le + 1:ri+1;

    }
};