= Solution
Use null to indicate that the requested key is absent:
``
private def find(name: String, head: Entry): Entry = {
var cursor = head
while (cursor != null && cursor.name != name) {
cursor = cursor.next
}
cursor
}
``
The <loop invariant> is that the skipped <string prefix> contains no entry with the requested name and `cursor` starts the unsearched <string suffix> of the unchanged bucket. Its remaining length is a <loop variant>. <Short-circuit evaluation> prevents accessing a null entry. On exit, either `cursor` is null and the whole bucket has been ruled out, or its name equals the key. \b[No <list> links or stored numbers are modified.] <String> comparison here uses value equality; node deletion elsewhere uses reference identity.
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