Given a list of words to insert and a single pattern to search for, decide whether any inserted word matches it — where the pattern may contain '.', a wildcard that matches any single letter in that position. A pattern with no dots at all is just an ordinary exact-word lookup. An ordinary trie walk follows exactly one child per character. A wildcard breaks that: at a '.', there's no single "next node" to commit to, so the search has to try every existing child and recurse into each — backtracking out of any branch that doesn't eventually pan out, and returning true the instant one does. Positions without a dot are still cheap, single-child steps; it's only the wildcards that fan the search out.