559. Maximum Depth of N-ary Tree*

559. Maximum Depth of N-ary Tree*

https://leetcode.com/problems/maximum-depth-of-n-ary-tree/

题目描述

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.

Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).

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 height of the n-ary tree is less than or equal to 1000
• The total number of nodes is between [0, 10^4]

C++ 实现 1

递归的方式.

/*
// 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) {
        if (!root) return 0;
        int res = 0;
        for (auto &c : root->children)
            res = std::max(res, maxDepth(c));
        res += 1;
        return res;
    }
};

C++ 实现 2

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

    Node() {}

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/
class Solution {
public:
    int maxDepth(Node* root) {
        return depth(root);
    }
private:
    int depth(Node *root) {
        if (!root) return 0;
        int res = 1;
        for (auto &ch : root->children)
            res = max(res, depth(ch) + 1);
        return res;
    }
};