# 1522. Diameter of N-Ary Tree
###### tags: `Leetcode` `Medium` `DFS` `FaceBook`
Link: https://leetcode.com/problems/diameter-of-n-ary-tree/
## 思路
随时记录每个maxLen,也就是所有child进入maxDepth()函数之后返回的值当中最大的两个求和
最大的两个这里是用array维护的~ 也可以用priority queue最小堆

maxDepth返回以这个node为root的最长分支的长度
## Code

class Solution {
    int maxDiameter = 0;
    public int diameter(Node root) {
        dfs(root);
        return maxDiameter;
    }
    private int dfs(Node root){
        if(root == null) return 0;
        int[] maxLen = new int[2];
        for(Node child:root.children){
            int len = dfs(child)+1;
            if(len>maxLen[1] && len>maxLen[0]){
                maxLen[1] = maxLen[0];
                maxLen[0] = len;
            }
            else if(len>maxLen[1]) maxLen[1] = len;
        }
        maxDiameter = Math.max(maxDiameter, maxLen[0]+maxLen[1]);
        return maxLen[0];
    }
}