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]
Constraints:
The height of the n-ary tree is less than or equal to 1000 The total number of nodes is between [0, 10^4]
/*
// Definition for a Node.
public class Node {
public int val;
public IList<Node> children;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val,IList<Node> _children) {
val = _val;
children = _children;
}
}
*/
public class Solution {
IList<int> result = new List<int>();
public IList<int> Preorder(Node root) {
if(root==null){
return result;
}
result.Add(root.val);
foreach(var child in root.children){
Preorder(child);
}
return result;
}
}Time Complexity: O(n)
Space Complexity: O(1)
