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+# [559. Maximum Depth of N-ary Tree](https://leetcode-cn.com/problems/maximum-depth-of-n-ary-tree/)
+
+## 题目
+
+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**:
+
+![https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png](https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png)
+
+    Input: root = [1,null,3,2,4,null,5,6]
+    Output: 3
+
+**Example 2**:
+
+![https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png](https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png)
+
+    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.
+
+## 题目大意
+
+给定一个 N 叉树，找到其最大深度。
+
+最大深度是指从根节点到最远叶子节点的最长路径上的节点总数。
+
+N 叉树输入按层序遍历序列化表示，每组子节点由空值分隔（请参见示例）。
+
+## 解题思路
+
+- 使用广度优先遍历
+
+## 代码
+
+```go
+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
+}
+```
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