Faster LinkedHashSet head() #2728
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While writing up vavr-io#2727 I noticed that `LinkedHashSet.head()` is implemented `iterator().head()`. This is inefficient because `queue.iterator().next()` makes a call to `.head()`, but also to `.tail()` so as to prepare for the next `head()` call. Given the structure of the underlying `Queue`, the `head()` call is worst case `O(1)` but the tail call is worst case `O(n)`. The present worst case will be achieved if there have never been overwrites or removals from the set, which is probably a fairly common case.
danieldietrich
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Jan 3, 2023
pivovarit
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While writing up #2727 I noticed that `LinkedHashSet.head()` is implemented `iterator().head()`. This is inefficient because `queue.iterator().next()` makes a call to `.head()`, but also to `.tail()` so as to prepare for the next `head()` call. Given the structure of the underlying `Queue`, the `head()` call is worst case `O(1)` but the tail call is worst case `O(n)`. The present worst case will be achieved if there have never been overwrites or removals from the set, which is probably a fairly common case.
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While writing up #2727 I noticed that
LinkedHashSet.head()is implemented byiterator().head(). This is inefficient becausequeue.iterator().next()makes a call to.head(), but also to.tail()so as to prepare for the nexthead()call. Given the structure of the underlyingQueue, thehead()call is worst caseO(1)but the tail call is worst caseO(n). The present worst case will be achieved if there have never been overwrites or removals from the set, which is probably a fairly common case.