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N-ary Tree Preorder Traversal

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Given an n-ary tree, return the preorder traversal of its nodes’ values.

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


Follow up:

Recursive solution is trivial, could you do it iteratively?


Example 1:

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

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: [1,2,3,6,7,11,14,4,8,12,5,9,13,10]



  • The height of the n-ary tree is less than or equal to 1000
  • The total number of nodes is between [0, 10^4]
Solution 1: Solution 2: