grind 75: symmetric-tree brute force sol

Author: kumar91gopi

README.md

@@ -337,6 +337,7 @@ solution of many challenges of [Leetcode](https://leetcode.com/), [Exercism](htt
 46. [3sum Closest](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/leetcode/grind75/3sum_closest.rb)
 47. [Min Stack](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/leetcode/grind75/min_stack.rb)
 48. [Balanced Binary tree](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/leetcode/grind75/balanced_binary_tree.rb)
+49. [Symmetric Tree](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/leetcode/grind75/symmetric_tree.rb)
 
 
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leetcode/grind75/symmetric_tree.rb

@@ -0,0 +1,34 @@
+# Problem: https://leetcode.com/problems/symmetric-tree/description/
+=begin
+Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).
+Input: root = [1,2,2,3,4,4,3]
+Output: true
+Input: root = [1,2,2,null,3,null,3]
+Output: false
+=end
+
+
+#Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val = 0, left = nil, right = nil)
+#         @val = val
+#         @left = left
+#         @right = right
+#     end
+# end
+# @param {TreeNode} root
+# @return {Boolean}
+
+#Solution 1 (Brute force Recursive)
+def is_symmetric(root)
+    return true if root.nil?
+    compare_subtrees(root.left,root.right)
+end
+
+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)
+end