Merge pull request #2046 from CodingTestStudy2/염혜정

[염혜정] Day18

Author: github-actions[bot]

leetcode3/염혜정/226. Invert Binary Tree.java

@@ -0,0 +1,15 @@
+// O(n)
+
+class Solution {
+    public TreeNode invertTree(TreeNode root) {
+        if (root == null) return null;
+
+        TreeNode temp = root.left;
+        root.left = root.right;
+        root.right = temp;
+
+        invertTree(root.left);
+        invertTree(root.right);
+        return root;
+    }
+}