max depth of binary tree

max_depth_of_binary_tree.cpp

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 * 
 * The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
 */
class Solution {
public:
    int maxDepth(TreeNode *root) {
        // max depth is this level (if present) plus max of its two sub-trees
        if (!root)
            return 0;
        return 1 + max(maxDepth(root->left), maxDepth(root->right));
    }
};