559. Maximum Depth of N-ary Tree

Given a n-ary 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.

For example, given a 3-ary tree:

We should return its max depth, which is 3.

Note:

1. The depth of the tree is at most 1000.

2. The total number of nodes is at most 5000.

解题要点：

找当前节点中child的递归次数，直到不能递归（说明无child），记录下来，最后返回这个值。

/*
// 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) {
        if(root == null) return 0;
        int res = 0;
        for(Node child : root.children)
            res = Math.max(res, maxDepth(child));
        return 1 + res;
    }
}