1. Find unique string (without repeating characters) from a given string. 2. Write a class to generate unique employee ID with A-Z,a-z,0-9. 3. You are given millisecond, convert into HH:MM:SS format from 12mid night. 4. Problem on Graph datastructure, to findout if possible loop with weight and distance. 5. Design questions, Puzzles. 6. Test Management questions.