Domain Score Accumulation (Reverse Trie)

Coding round. Each domain (at any level) carries a score; the score of a leaf hostname is the sum of scores along its suffix hierarchy (e.g. `mail.domain.com = score(mail.domain.com) + score(domain.com) + score(com)`). Build a reverse trie keyed on the dotted labels read right-to-left and DFS / backtrack to accumulate each leaf's full hostname and summed score. Interviewers may insist the score live in a separate map rather than inside the trie node. Requirements Each domain string maps to an integer score. Domains are hierarchical by dot-separated labels (com, domain.com, mail.domain.com). The score of any leaf hostname is the sum of the scores of every domain on its suffix chain, from the full hostname up to the top-level label. Output the accumulated score for each leaf domain. Examples com 20 domain.com 10 mail.domain.com 5 test.com 10 user.test.com 30 contact.user.test.com -5 mail.domain.com = 5 + 10 + 20 = 35 contact.user.test.com = -5 + 30 + 10 + 20 = 55 Notes Build the trie on labels read right-to-left (com is the root child, then domain, then mail), so each path from root to a node spells a domain by its suffix hierarchy. Accumulate the running score down the path; a leaf node emits joined_labels plus the path sum. Scores can be negative — do not assume monotonic growth down the tree. A reported interviewer constraint: keep the per-domain score in a separate structure keyed by the node rather than as a field on the trie node itself. Ask up front where the score should live; reworking this mid-round is what cost one candidate the dry-run time. A flat hashmap (hostname → score) with suffix walking also works, but the interviewer here specifically steered toward the trie + DFS framing. Preparation Implement the reverse trie: split on ., insert reversed, store score in a side map, then DFS reconstructing the dotted hostname and summing along the path. Practice both layouts (score-in-node vs score-in-side-map) so an interviewer steering you to the second one does not cost you rewrite time.