Following is the list of questions which I can recall - 1. Find All Palindromes in a String, considering all cases. If possible using Collections 2. Sort a stack (implemented using an array) in an optimal way 3. Find number of (0)s and 1(s) in an array having only 0(s) and 1(s) 4. Sort an array having 0(s), 1(s) and 2(s) 5. Explain architecture of the Selenium based automation framework 6. How to test multiple WSDLs? What all test cases or testing methods can be applied 7. How to use multi-threading concept in your automation framework 8. What are immutable classes 9. How to implement a queue with synchronized collections(which collection can be used and why) 10. Page Object Model vs Page Factory Model 11. Singleton Class and concept of private constructor 12. How to handle same object with different properties across different browsers in Selenium based Automation Framework?

Linked list and tree based questions