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plurals

PO
primarykey
Id
9074056
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2012-01-31T03:38:48.733
FavoriteCount
0
LastActivityDate
2017-09-16T13:48:58.623
LastEditDate
2017-09-16T13:48:58.623
LastEditorUserId
14860
OwnerUserId
14860
ParentId
9073903
PostTypeId
2
Score
16
ViewCount
0
LastEditorDisplayName
text
Body
A bucket is simply a fast-access location (like an array index) that is the the result of the hash function. The idea with hashing is to turn a complex input value into a different value which can be used to rapidly extract or store data. Consider the following hash function for mapping people's names into street addresses. First take the lower-cased initials from the first and last name and turn them both into numeric values (0 through 25, from 'a' through 'z'). Multiply the first by 26 and add the second, and this gives you a value from 0 to 675 (26 * 26 distinct values, or bucket IDs). This bucket ID is then to be used to store or retrieve the information. Now you can have a perfect hash (where each allowable input value maps to a distinct bucket ID) so that a simple array will suffice for the buckets. In other words, you maintain an array of 676 street addresses and use the bucket ID to find the one you want: <pre><code>+-------------------+ | George Washington | -> hash(GW) +-------------------+ | +-> GwBucket[George's address] +-------------------+ | Abraham Lincoln | -> hash(AL) +-------------------+ | +-> AlBucket[Abe's address] </code></pre> Or you can have an imperfect hash (such as one where John Smith and Jane Seymour would end up with the same bucket ID). In that case, you need a more complex backing data structure than a simple array, to maintain a collection of addresses. This could be as simple as a linked list, or as complex as yet another hash: <pre><code>+------------+ +--------------+ | John Smith | | Jane Seymour | +------------+ +--------------+ | | V V hash(JS) hash(JS) | | +-----> JsBucket <----+ \/ +-----------------------------------+ | "John Smith -> [John's address] | | "Jane Seymour -> [Jane's address] | +-----------------------------------+ </code></pre> Then, as well as the initial hash lookup, an extra level of searching needs to be carried out within the bucket itself, to find the specific information.
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1. POWhat does "bucket entries" mean in the context of a hashtable?
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1. USpaxdiablo
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1. USpaxdiablo
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