Merge pull request neetcode-gh#1963 from laitooo/0617-merge-two-binar…

…y-trees.dart

Create: 0617-Merge-Two-Binary-Trees.dart

dart/0617-merge-two-binary-trees.dart

@@ -0,0 +1,24 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *   int val;
+ *   TreeNode? left;
+ *   TreeNode? right;
+ *   TreeNode([this.val = 0, this.left, this.right]);
+ * }
+ */
+class Solution {
+  TreeNode? mergeTrees(TreeNode? root1, TreeNode? root2) {
+      if (root1 == null && root2 == null) {
+          return null;
+      }
+
+      int val1 = (root1 == null) ? 0 : root1.val;
+      int val2 = (root2 == null) ? 0 : root2.val;
+      TreeNode res = TreeNode();
+      res.val = val1 + val2;
+      res.left = mergeTrees((root1 == null) ? null : root1.left, (root2 == null) ? null : root2.left);
+      res.right = mergeTrees((root1 == null) ? null : root1.right, (root2 == null) ? null : root2.right);
+      return res;
+  }
+}