pre-order-traversal.js

/*
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]
*/

var preorder = function(root) {

    let arr = [];

    const traverse = (root) => {
        if(!root) return;

        arr.push(root.val);
        for(let i = 0; i < root.children.length; i++) {
            traverse(root.children[ i ]);
        }

    };

    traverse(root);
    return arr;
};