LeetCode 559 Maximum Depth of N-ary Tree

给予树：
         1 
       / | \ 
      3  2  4
     / \ 
    5   6 
返回深度 3.

/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val,List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/
class Solution {
    public int maxDepth(Node root) {
        int depth = 1;
        if (root == null)
            return 0;
        for (Node n : root.children){
            depth = Math.max(depth, maxDepth(n) + 1);
        }
        return depth;
    }
}