Every leetcoder knows that just by looking at the problem contraints we can immediately know which algorithms can be employed and which can be thrown out.
For example, given a collection of elements with a size < 10, we already know that we can check every permutation, < 20 - check every subset, < 100 - n^3, 1000 - n^2, 1000000 - up t O(nlogn) and so on.
Will interviewers reveal the contstraints if asked? Or will they just say to lay out everything we can come up with?