Merge pull request #2595 from fahim041/0144-binary-tree-preorder-trav…

…ersal.ts

create: 0144-binary-tree-preorder-traversal.ts

typescript/0144-binary-tree-preorder-traversal.ts

@@ -0,0 +1,30 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function preorderTraversal(root: TreeNode | null): number[] {
+    let res: number[] = [];
+
+    function dfs(root) {
+        if (!root) {
+            return;
+        }
+
+        res.push(root.val);
+        dfs(root.left);
+        dfs(root.right);
+    }
+
+    dfs(root);
+    return res;
+}