Maximum Depth of N-ary Tree

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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

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      1
    / | \
   3  2  4
  / \
 5   6

Input: root = [1,null,3,2,4,null,5,6]
Output: 3

Example 2

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        1
     / | | \
    2  3 4  5
      /| |  |\
     6 7 8  9 10
       | |  | 
      11 12 13
       |
      14

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

My Answer

  • 재귀를 이용
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/*
// 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 max_depth = 0;
        for(Node node : root.children ) {
            max_depth = Math.max(max_depth, maxDepth(node));            
        }
        
        return max_depth +1;
    }
}

참고