Update stack.md

contents/algorithms/stack.md

@@ -11,3 +11,8 @@ title: Stack
   - E.g. `{ac[bb]}`, `[dklf(df(kl))d]{}` and `{[[[]]]}` are matched. But `{3234[fd` and `{df][d}` are not.
   - [Source](http://blog.gainlo.co/index.php/2016/09/30/uber-interview-question-delimiter-matching/)
 - Sort a stack in ascending order using an additional stack.
+
+## Complexity
+
+- Access , Search O(N)
+- Insertion , Deletion O(1)