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[学习笔记] leetcode 559. Maximum Depth of N-ary Tree

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发表于 2019-12-24 11:49:09 | 显示全部楼层 |阅读模式

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  1. Given a n-ary tree, find its maximum depth.

  2. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

  3. Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).



  4. Example 1:

  5. 1.jpg

  6. Input: root = [1,null,3,2,4,null,5,6]
  7. Output: 3
  8. Example 2:

  9. 2.jpg

  10. 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]
  11. Output: 5


  12. Constraints:

  13. The depth of the n-ary tree is less than or equal to 1000.
  14. The total number of nodes is between [0, 10^4].
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  1. /*
  2. // Definition for a Node.
  3. class Node {
  4.     public int val;
  5.     public List<Node> children;

  6.     public Node() {}

  7.     public Node(int _val) {
  8.         val = _val;
  9.     }

  10.     public Node(int _val, List<Node> _children) {
  11.         val = _val;
  12.         children = _children;
  13.     }
  14. };
  15. */
  16. class Solution {
  17.    
  18.     int max;
  19.     public int maxDepth(Node root) {
  20.         if(root == null) return 0;
  21.         
  22.         int dep = 1;
  23.         dfs(root,dep);
  24.         return max;
  25.     }
  26.    
  27.     public void dfs(Node root, int depth){
  28.         if(depth > max) max = depth;
  29.         if(root.children.size() == 0) return;
  30.         int len = root.children.size();
  31.         
  32.         for(int i = 0; i< len; i++){
  33.             if(root.children.get(i) != null){
  34.                 dfs(root.children.get(i), depth+1);
  35.             }
  36.         }
  37.     }
  38. }
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