Leetcode 809. Expressive Words

Count how many words can be transformed into s by expanding letter groups: a word is stretchy if it has the same sequence of character groups as s and for each group either the counts are equal or s's group count is at least 3 and no smaller than the word's count. The core challenge is matching run-length-encoded groups (or using two-pointer group comparisons) and validating the count conditions for each word.