559. Maximum Depth of N-ary Tree

1. Question

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).

2. 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

3. 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.

4. References

来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/maximum-depth-of-n-ary-tree 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

5. Solutions

class Solution {
  public int maxDepth(Node root) {
    int ans = 0;
    if (root == null) {
      return ans;
    }

    List<Node> children = root.children;
    for (Node child : children) {
      ans = Math.max(ans, maxDepth(child));
    }

    return ans + 1;
  }
}