104. 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.

Solution：递归post-order dfs来upwards累积

Time Complexity: O(N) Space Complexity: O(N) 递归缓存

Solution Code：

class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
    }
}