#161 · #3481 · Apply Substitutions(应用替换)

You are given replacements, a list of [key, value] pairs where each key is a single uppercase letter and the value may contain placeholders of the form %X%. Given a text containing such placeholders, expand every placeholder recursively and return the resulting string. Constraints: 1 <= replacements.length <= 26; all keys are distinct; substitutions are guaranteed to terminate.