solves n ary tree preorder traversal

Author: anishLearnsToCode

Diff for: README.md

@@ -153,7 +153,7 @@
 | 572 | [Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree) | Easy | [![Java](assets/java.png)](src/SubtreeOfAnotherTree.java) [![Python](assets/python.png)](python/subtree_of_another_tree.py) |
 | 575 | [Distribute Candies](https://leetcode.com/problems/distribute-candies) | Easy | [![Java](assets/java.png)](src/DistributeCandies.java) [![Python](assets/python.png)](python/distribute_candies.py) |
 | 581 | [Shortest Unsorted Continuous Subarray](https://leetcode.com/problems/shortest-unsorted-continuous-subarray) | Medium | [![Java](assets/java.png)](src/ShortestUnsortedContinuousSubarray.java) [![Python](assets/python.png)](python/shortest_continuous_unsorted_subarray.py) |
-| 589 | [N-Ary Tree Preorder Traversal](https://leetcode.com/problems/n-ary-tree-preorder-traversal) | Easy | |
+| 589 | [N-Ary Tree Preorder Traversal](https://leetcode.com/problems/n-ary-tree-preorder-traversal) | Easy | [![Java](assets/java.png)](src/NArayTreePreOrderTraversal.java) [![Python](assets/python.png)](python/n_ary_tree_preorder_traversal.py) |
 | 590 | [N-Ary Tree Postorder Traversal](https://leetcode.com/problems/n-ary-tree-postorder-traversal) | Easy | |
 | 594 | [Longest Harmonious Subsequence](https://leetcode.com/problems/longest-harmonious-subsequence) | Easy | |
 | 598 | [Range Addition II](https://leetcode.com/problems/range-addition-ii) | Easy | |

Diff for: python/n_ary_tree_preorder_traversal.py

@@ -0,0 +1,23 @@
+# Definition for a Node.
+from typing import List
+
+
+class Node:
+    def __init__(self, val=None, children=None):
+        self.val = val
+        self.children = children
+
+
+class Solution:
+    def __init__(self):
+        self.result = []
+
+    def preorderTraversal(self, root: Node) -> None:
+        if root is None: return None
+        self.result.append(root.val)
+        for child in root.children:
+            self.preorderTraversal(child)
+
+    def preorder(self, root: Node) -> List[int]:
+        self.preorderTraversal(root)
+        return self.result

Diff for: src/NArayTreePreOrderTraversal.java

@@ -0,0 +1,19 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class NArayTreePreOrderTraversal {
+    List<Integer> result = new ArrayList<>();
+
+    public List<Integer> preorder(Node root) {
+        preorderTraversal(root);
+        return result;
+    }
+
+    private void preorderTraversal(Node root) {
+        if (root == null) return;
+        result.add(root.val);
+        for (Node child :root.children) {
+            preorderTraversal(child);
+        }
+    }
+}