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by Sumit Chourasia | Oct 07, 2020 | Category :coding | Tags : algorithm binary-tree data-structure easy leetcode tree

N-ary Tree Postorder Traversal - Tree - Easy - LeetCode

N-ary Tree Postorder Traversal - Tree - Easy - LeetCode

Given an n-ary tree, return the postorder 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: [5,6,3,2,4,1]
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: [2,6,14,11,7,3,12,8,4,13,9,10,5,1]
 

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> Postorder(Node root) {
        if(root == null){
            return result;
        }
        
        foreach(var child in root.children){
            Postorder(child);
        }
        result.Add(root.val);
        return result;
    }
}

Time Complexity: O(n)

Space Complexity: O(1)

Contributed By: Sumit Chourasia
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