LeetCode104 Maximum Depth of Binary Tree 二叉搜索树的最大深度

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.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

题源：here；完整实现：here

思路：

递归遍历二叉树，每一次递归层数加一。代码如下：

int maxDepth(TreeNode* root) {
	if (!root) return 0;
	return max(maxDepth(root->left), maxDepth(root->right)) + 1;
}