It seems questions that involve a DS to solve, are comparatively easier to at least begin with. For questions that are pure logic, it takes time to come up with a solution and later implement it. For example, we know that the task of finding the largest number in an array on every query, after insertion of an arbitrary element, can be solved by using a Priority Queue. Now whenever I see a task involving this example as a sub-task, I at least have a start for the question. Similarly, there are many useful and known Data Structures that we use on a daily basis, like Segment Trees, BSTs, and many more.
I'd love to know some less known DS for pretty common tasks, if there exist such DS. I recently read about Wavelet tree, and I think they are really useful. How wonderful would it be, if there was a DS that dealt with sub-sequences or sub-arrays of an array(such questions are really irritating) or maybe something cool that isn't very common. I know the Chinese community has a lot of Data Structures that we don't even know about. I hope they can provide some help. Also, if someone would like to add some real cool tricks and techniques that solve some frequently occurring questions easily, you're most welcome!