559. Maximum Depth of N-ary Tree

问题：

给定N叉树，求该树的最大深度。

Example 1:
Input: root = [1,null,3,2,4,null,5,6]
Output: 3

Example 2:
Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: 5
 
Constraints:
The depth of the n-ary tree is less than or equal to 1000.
The total number of nodes is between [0, 104].

　　

example 1:

example 2:

解法：BFS

将root节点入队，

每次遍历当前节点的所有children节点，入队，

遍历queue的层数，即为所求。

代码参考：

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

    Node() {}

    Node(int _val) {
        val = _val;
    }

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
public:
    int maxDepth(Node* root) {
        int res = 0;
        queue<Node*> q;
        if(root) q.push(root);
        while(!q.empty()) {
            int sz = q.size();
            for(int i=0; i<sz; i++) {
                Node* cur = q.front();
                q.pop();
                for(Node* c:cur->children) {
                    if(c) q.push(c);
                }
            }
            res++;
        }
        return res;
    }
};