hashtable

问题 How does google's sparse hash table handle collisions? i.e. when 2 elements map to the same bucket, how does it decide where to put the new (colliding) element? I'm reading What is the main implementation idea behind sparse hash table? but that answer doesn't cover the collision idea. 回答1: Your question is answered in the documentation here, specifically: 2c) If t.sparsetable[i % 32] is assigned, but to a value other than foo, look at t.sparsetable[(i+1) % 32] . If that also fails, try t

问题 If my intention is only to have a good hash function that spreads data evenly into all of the buckets, then I need not come up with a family of hash functions, I could just do with one good hash function, is that correct? The purpose of having a family of hash functions is only to make it harder for the enemy to build a pathological data set as when we pick a hash function randomly, he/she has no information about which hash function is employed. Is my understanding right? EDIT: Since someone

问题 I was wondering how you declare a hashtable in powershell with an initial capacity. I know how large I want it to be but I have to assign the values to it in a loop. So something like: $hashtable = @{} (100) 回答1: JeroenMostert makes a good point as to why you may not need to specify an initial capacity: Be aware that pre-specifying the capacity usually doesn't win you much in terms of memory or runtime, though; it already implements generous dynamic sizing, and if your guess is off, the

问题 I have a hashtable whose keys are of type integer, however when deserializing using json.net the keys come back as strings, is there a way to keep the key type on hashtable using json.net serialization/deserialization? This hashtable is a property of the type 'MyType' var settings = new JsonSerializerSettings(); settings.TypeNameHandling = TypeNameHandling.Objects; string json = JsonConvert.SerializeObject(o, Formatting.Indented, settings); mo = JsonConvert.DeserializeObject<MyType>(json, new

问题 I have created a program using the built in java.util.hashtable but now I need to resolve collisions using separate chaining. Is it possible with this implementation of a hashtable? Is there one out there already implemented that uses separate chaining? 回答1: Looking at the source of the Hashtable implementation, it looks like it already uses separate chaining. If you look at the Entry<K,V> class starting at line 901, you'll see that it has a reference to another Entry named next . If you then

问题 In vb.net / winforms, how can a hashtable be bound to a drop down list or any other datasource-driven control? 回答1: Is this winforms, wpf, or asp.net? [update: ahh... winforms ;-p] winforms wants data to be IList (or, indirectly, via IListSource ) - so I'm guessing (from the comment) that you are using winforms. None of the inbuilt dictionary-like collections implement IList , but to be honest it doesn't matter: if you are data-binding, the volume is probably fairly small, so a regular list

问题 Anyone have any ideas why the following code would produce an error, see additional comments after the function for more details function callee ([Hashtable]$arg0) { [Hashtable]$hashtable = @{} $hashtable = $arg0 $hashtable.add('passed', $True) # $hashtable ######## toggle this line $type = $hashtable.GetType() Write-Host "$type" return $hashtable } function caller { [Hashtable]$hashtable = @{'00'='0'} $hashtable = callee $hashtable ##### returns error here $hashtable.add('returned', $True)

问题 I have recently been working with hash tables in Common Lisp. I have been wondering how to make a separate copy of a hash table containing all the same values as the first. Is there an official way to do this? If not, can you give me an example using maphash? 回答1: As clhs does not list a copy table function I'd assume that maphash is the way to go. (defun copy-table (table) (let ((new-table (make-hash-table :test (hash-table-test table) :size (hash-table-size table)))) (maphash #'(lambda(key

问题 The best look-up structure is a HashTable . It provides constant access on average (linear in worst case). This depends on the hash function. Ok. My question is the following. Assuming a good implementation of a HashTable e.g. HashMap is there a best practice concerning the keys passed in the map?I mean it is recommended that the key must be an immutable object but I was wondering if there are other recommendations. Example the size of the key? For example in a good hashmap (in the way

问题 I have a map X and I'm trying to get a set of the keys satisfying a certain condition, something like this: Map.Keys X |> Set.filter (fun x -> ...) ...but I cannot find the way to get the keys from F#'s Map collection. 回答1: Convert your map to sequence of tuples (key,value) first and then map it to a sequence of just keys: map |> Map.toSeq |> Seq.map fst FSI sample: >Map.ofList[(1,"a");(2,"b")] |> Map.toSeq |> Seq.map fst;; val it : seq<int> = seq [1; 2] Or alternatively, as ordering of keys