Create 0144-binary-tree-preorder-traversal.js

Author: aadil42

Diff for: javascript/0144-binary-tree-preorder-traversal.js

@@ -0,0 +1,27 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * Pre-order-traversal
+ * Time O(n) | Space O(n)
+ * https://leetcode.com/problems/binary-tree-preorder-traversal/
+ * @param {TreeNode} root
+ * @return {number[]}
+ */
+var preorderTraversal = function(root) {
+    
+    const dfs = (node, pre) => {
+        if(!node) return pre;
+        pre.push(node.val);
+        dfs(node.left, pre);
+        dfs(node.right, pre);
+        return pre;
+    }
+
+    return dfs(root, []);
+};