JFrog Software Developer interview questions

Your program have to support following operations: 1. Receive a character as an input and add it to all previous characters that were sent to this method 2. Remove list of characters from index x till index y 3. Print all the remaining elements in the order they were sent All 3 methods can be used more than one time, and in any order the user wants Example: add(a) add(b) add(c) add(d) remove (2-3) print - the result should be ad He wanted to see what data structure will I pick for the initial (naive) implementation and what will be the complexity for every action. After that he asked me to try and make it a little bit more efficient.