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559. Maximum Depth of N-ary Tree

中文文档

Description

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 total number of nodes is in the range [0, 104].
• The depth of the n-ary tree is less than or equal to 1000.

Solutions

Solution 1

Python3

"""
# Definition for a Node.
class Node:
    def __init__(self, val=None, children=None):
        self.val = val
        self.children = children
"""


class Solution:
    def maxDepth(self, root: 'Node') -> int:
        if root is None:
            return 0
        return 1 + max([self.maxDepth(child) for child in root.children], default=0)

Java

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

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

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

class Solution {
    public int maxDepth(Node root) {
        if (root == null) {
            return 0;
        }
        int ans = 1;
        for (Node child : root.children) {
            ans = Math.max(ans, 1 + maxDepth(child));
        }
        return ans;
    }
}

C++

/*
// 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 ans = 1;
        for (auto& child : root->children) ans = max(ans, 1 + maxDepth(child));
        return ans;
    }
};

Go

/**
 * Definition for a Node.
 * type Node struct {
 *     Val int
 *     Children []*Node
 * }
 */

func maxDepth(root *Node) int {
	if root == nil {
		return 0
	}
	ans := 1
	for _, child := range root.Children {
		ans = max(ans, 1+maxDepth(child))
	}
	return ans
}