feat: solve new question

Author: arwildo

invert-binary-tree/main.js

@@ -0,0 +1,36 @@
+/**
+ * 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)
+ * }
+ */
+ /*
+        [4,2,7,1,3,6,9]
+        
+              4
+             / \
+            2   7
+           / \  / \
+          1  3 6   9
+ 
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+var invertTree = function(root) {
+    if (root === null) return null;
+
+    // swap the children
+    let tmp = root.left;
+    root.left = root.right;
+    root.right = tmp;
+
+    // do it again until root of the tree
+    invertTree(root.left);
+    invertTree(root.right);
+
+    return root;
+};