LeetCode刷题记录：104. 二叉树的最大深度

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if (root == NULL) {
        	return 0;
		}
		
		int left = maxDepth(root->left);
		int right = maxDepth(root->right);
		
        return max(left, right) + 1;
    }
};