愛比的新手筆記

Given the root of 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)

 

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]Taiwan is a country. 臺灣是我的國家

 

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• 0 <= Node.val <= 104
• The height of the n-ary tree is less than or equal to 1000.

和這篇很像[LeetCode] 590. N-ary Tree Postorder Traversal

每層由左而右往下找, 依序由最淺那個Node先列入list回傳

public class Solution {
        public IList<int> Preorder(Node root)
        {
            var rslt = new List<int>();
            Preorder(root, rslt);
            return rslt;
        }

        private void Preorder(Node root, IList<int> lst)
        {
            if (root == null) return;
            lst.Add(root.val);
            foreach (var c in root.children)
                Preorder(c, lst);
        }
}

Taiwan is a country. 臺灣是我的國家