A suggestion box wants several options, not one, so today you widen each node's cache from its single best completion into a small ranked top list, still maintained as terms are added.
Cache a bounded, ranked top list of completions at each node, kept current on every Add.
One suggestion is rarely enough, so widen the cache: replace each node’s single
best with a cache slice holding its top few completions in ranked order,
capped at a fixed capacity (cacheCap). Add maintains it the same way - for
each node on the term’s path, drop any stale entry for that term, insert the new
one, re-rank, and trim back to the cap. Best becomes a one-liner over
cache[0], so the previous lesson’s guarantee still holds.
Dropping a stale entry before inserting is what makes this survive a term being
re-added with a new weight (and, soon, a selection bumping it): without it the
cache would hold two rows for the same term. Capping at cacheCap keeps every
node’s memory bounded no matter how large its subtree - the cache is a fast lane
for the common small request, and the next lesson wires the ranked query to read
from it, falling back to a full scan only when a caller asks for more than the cap.
const cacheCap = 5 // keep at most this many per node// node gains: cache []Completion (replaces best; Best returns cache[0].Term)func updateCache(n *node, term string, weight int) {out := n.cache[:0]for _, c := range n.cache { // drop any stale entry for this termif c.Term != term { out = append(out, c) }}out = append(out, Completion{term, weight})sort.Slice(out, func(i, j int) bool { return ranks(out[i], out[j]) })if len(out) > cacheCap { out = out[:cacheCap] }n.cache = out}