hashtable | 易学教程

How to Store unique objects to avoid the duplicates in java Set?

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问题 How to Store unique objects to avoid the duplicates in java Set? For example Consider Employee object which (Employee Id, name, salary....) list of employee of objects need to add in the Set. We need to restrict the Set for the duplicate elements which need to identify by the "Employee Id. What are the best way's to do? 回答1: If you are using an implementation of a java.util.Set , it should not allow duplicates as long as your equals and hashCode methods are implemented properly. Not sure why

Run Time for Linear Probing on Hash table

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问题 what is the running time (big Oh) for linear probing on insertion, deletion and searching. Thanks 回答1: Theoretical worst case is O(n) since if you happen to insert all the elements such that they consecutively collide then the last element inserted will have to be put into the table n steps from its original hash position. You could however calculate the average expected number of steps if you know the distribution of your input elements (possibly assuming random, but of course assumption is

Is it possible to initialize a .NET type with properties?

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问题 For example I want use this class Microsoft.HyperV.PowerShell.HardDiskDrive I tried to initialize it by this way: $obbb = [Microsoft.HyperV.PowerShell.HardDiskDrive]@{ Path = 'D:\\TEST\\test\\Virtual Hard Disks\\test.vhdx' DiskNumber = $null MaximumIOPS = '1000' MinimumIOPS = '0' QoSPolicyID = '00000000-0000-0000-0000-000000000000' SupportPersistentReservations = $false WriteHardeningMethod = '0' ControllerLocation = '0' ControllerNumber = '0' ControllerType = '0' Name = 'Hard Drive on IDE

Hashtable. Name history. Why not HashTable?

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问题 we know: ArrayList; LinkedList; TreeMap and other... and all names in CamelCase format, but why Hashtable , not HashTable ? it is unprincipled question, just wondering :) 回答1: Hashtable was created in Java v1. The consistent naming conventions for collections were established later, in Java2, when the other classes were published as part of the brand new Java Collection Framework. Which btw made Hashtable obsolete, so it should not be used in new code. 回答2: It's a typo. Same as Cloneable

how to get the keys of a xmlHashTable ? (libxml2)

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I am using the library libxml2 to parse an XML document. And then I saw xmlHashTable in this library. Is it possible to get all the keys of a xmlHashTable ? I want to store all the keys in an array. The XML document is: <?xml version="1.0" encoding="UTF-8"?> <?type-proto key="MIPRegistrationRequest" value="mip" ?> <?avp-proto key="Example-AVP" value="data" ?> <!DOCTYPE dictionary SYSTEM "dictionary.dtd" [  <!ENTITY nasreq SYSTEM "nasreq.xml"> <!ENTITY eap SYSTEM "eap.xml"> <!ENTITY mobileipv4 SYSTEM

Powershell: replacing in strings using a hashtable

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问题 Okay, so I've set up a hash table with names being what to replace and keys being what to replace with, like this: $r = @{ "dog" = "canine"; "cat" = "feline"; "eric" = "eric cartman" } What should I do next? I've tried this: (Get-Content C:\scripts\test.txt) | Foreach-Object { foreach ( $e in $r.GetEnumerator() ) { $_ -replace $e.Name, $e.Value } } | Set-Content C:\scripts\test.txt.out But it doesn't work at all, it just writes each line three times, without replacing anything. EDIT: Contains

What happens if hashcode calculated exceeds the INTEGER MAX LIMIT?

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问题 Here is the hashCode() implementation from Java HashTable Class. What if the number of elements in the hashtable is huge and the hashcode exceeds the INTEGER MAX LIMIT -2,147,483,648 to 2,147,483,647 ? I assume hashCodes will be positive integers. public synchronized int hashCode() { int h = 0; if (count == 0 || loadFactor < 0) return h; // Returns zero loadFactor = -loadFactor; // Mark hashCode computation in progress Entry[] tab = table; for (int i = 0; i < tab.length; i++) for (Entry e =

Binary Search and Hashtable Search

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问题 I wanted to find out the trade off point between a Dictionary lookup and a binary search lookup of an array. I was expecting constant time lookups for the Dictionary, and logarithmic time lookups for the binary search depending on the size of the collection, with the binary search performing better for smaller sized collections. However, I was surprised when I saw the following results: I was surprised at: 1. Binary search is growing logarithmically at first, and then grows much faster. 2.

Hash Table and Substring Matching

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问题 I have hundreds of keys for example like: redapple maninred foraman blueapple i have data related to these keys, data is a string and has related key at the end. redapple: the-tree-has-redapple maninred: she-saw-the-maninred foraman: they-bought-the-present-foraman blueapple: it-was-surprising-but-it-was-a-blueapple i am expected to use hash table and hash function to record the data according to keys and i am expected to be able to retieve data from table. i know to use hash function and

Create a List<string> from HashTable keys?

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问题 Hey, how could I do this as short as possible? Thanks :-) 回答1: Try this: System.Collections.Hashtable ht = new System.Collections.Hashtable(); List<string> list = ht.Keys.Cast<string>().ToList(); 来源： https://stackoverflow.com/questions/3297558/create-a-liststring-from-hashtable-keys