Determine if one string is a subsequence of another. That is, check if you can form the first string by deleting characters from the second string without changing the order of the remaining characters.

Given an array of scores, assign medals (Gold, Silver, Bronze) to the top three scores and rank numbers to the rest. Return the rank list as an array of strings.

Find the length of the longest subsequence within a given sequence such that the differences between adjacent numbers alternate between positive and negative.