559. Maximum Depth of N-ary Tree #

Problem #

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, 10000].
• The depth of the n-ary tree is less than or equal to 1000.

Problem Summary #

Given an N-ary tree, find its maximum depth.

The maximum depth is the total number of nodes on the longest path from the root node to the farthest leaf node.

The N-ary tree input is serialized in level-order traversal, with each group of child nodes separated by a null value (see examples).

Solution Approach #

• Use breadth-first traversal

Code #

package leetcode

type Node struct {
	Val int
	Children []*Node
}

func maxDepth(root *Node) int {
	if root == nil {
		return 0
	}
	return 1 + bfs(root)
}

func bfs(root *Node) int {
	var q []*Node
	var depth int
	q = append(q, root.Children...)
	for len(q) != 0 {
		depth++
		length := len(q)
		for length != 0 {
			ele := q[0]
			q = q[1:]
			length--
			if ele != nil && len(ele.Children) != 0 {
				q = append(q, ele.Children...)
			}
		}
	}
	return depth
}