miinor update in symmetric tree

Author: kumar91gopi

leetcode/grind75/symmetric_tree.rb

@@ -28,7 +28,10 @@ def is_symmetric(root)
 
 def compare_subtrees(left_tree,right_tree)
     return true if left_tree.nil? and right_tree.nil?
-    return false unless (left_tree&.val == right_tree&.val)
-    return false unless compare_subtrees(left_tree&.right,right_tree&.left)
-    compare_subtrees(left_tree&.left,right_tree&.right)
+    return false if eft_tree.nil? or right_tree.nil?
+    return false unless (left_tree.val == right_tree.val)
+    return false unless compare_subtrees(left_tree.right,right_tree.left)
+    compare_subtrees(left_tree.left,right_tree.right)
 end
+
+# Solution 2 (Using BFS)