Easy - reverse a string, determine if a string is a palindrome, reverse the digits of an integer, determine if one string is an anagram of another.
Hard - implement a subset of regex match in optimal time+space, find the operations required to turn 1 word into another word given a list of transitory words, find the median of 2 sorted arrays in optimal time, find the next permuted value.
I think those "easy" examples are too easy to get any meaningful signal from. If they struggle, they have no idea what they're doing, and if they don't, you don't really learn anything about how they work because there's not much to them.
Other people have mentioned Triplebyte using console tic tac toe as a question; that seems like a better sort of "easy" question that still lets the interviewee have a chance to show off their problem solving and factoring skills.
