hashtable

问题 I have the following object and I want a dictionary to conditionally determine if there is a duplicate. For example, in one dictionary I only care about two properties being unique for my key. In a second dictionary, I want all the properties being unique for the key. Question 1: What interfaces should I override to accomplish this? (e.g. GetHashCode, IEqualityComparer, equals operator) Question 2: What should I do if I change a property that ultimately changes the value of the key? This is

问题 It's possible to color single hashtable column in powershell? For example color "Number" column to green: Number VMNic ------ ----- [0] vmnic0 [1] vmnic1 [2] vmnic2 [3] vmnic3 [4] vmnic4 [5] vmnic5 [6] vmnic6 [7] vmnic7 I create this output like that: [it's fragment from my code in the simplest way] $VMnics = get-vmhostnetworkadapter -Physical $NIC_collection = @() $VMnic_nr = "[$i]" Foreach ($VMnic in $VMnics){ $NIC_Details = New-Object PSObject $NIC_Details | Add-Member -Name Number -Value

问题 I don't understand how hash tables are constant time lookup, if there's a constant number of buckets. Say we have 100 buckets, and 1,000,000 elements. This is clearly O(n) lookup, and that's the point of complexity, to understand how things behave for very large values of n. Thus, a hashtable is never constant lookup, it's always O(n) lookup. Why do people say it's O(1) lookup on average, and only O(n) for worst case? 回答1: The purpose of using a hash is to be able to index into the table

问题 I need help creating a multidimensional HashMap or Hashtable in JSP. Why I do I need HashMap or HashTable? Because I ultimately want to pass back to the client a JSON object. If there is another way to ultimately arrive at a JSON object, I'm all ears. I also wanted to mention that this thread has been invaluable and I've been expanding on it: How can I write a multidimensional JSON object in JSP and pass the JSON object back to JavaScript? Here is what I want the result to looks like: {

问题 My instructor dumped this on us, and told us we just needed to google how to write a hash function. I am quite directionless on this. We wrote a basic Hash Table template for class, but I have a project due that requires ~160,000 strings to be sorted into a table with at least 500 buckets (I am wanting to do more for speed). I just have no idea where to look to get concise, easily digestible information on this. Any help would be greatly appreciated. 回答1: I suggest a universal hash function.

问题 If I have a key set of 1000, what is a suitable size for my Hash table, and how is that determined? 回答1: It depends on the load factor (the "percent full" point where the table will increase its size and re-distribute its elements). If you know you have exactly 1000 entries, and that number will never change, you can just set the load factor to 1.0 and the initial size to 1000 for maximum efficiency. If you weren't sure of the exact size, you could leave the load factor at its default of 0.75

问题 I'm currently trying to write an XML Parser with SAX and want to save the elements of an XML file into a Hashtable, but for this I need another one in that first table ( like this ): Hashtable<String, Hashtable<String, Set>> table; My question is whether its possible to address the second hashtable and, if so, how do I do this? 回答1: Do it like this: public static void main (String[] args) throws java.lang.Exception { Map<String, Map<String, Set<Integer>>> mapOfMaps = new Hashtable<String, Map

问题 My problem is, that i have a hash table which has about 1000000 entries and i need to find how many times a certain value appears in the hash table. key1-->val1 key2-->val2 key3-->val3 key4-->val1 key5-->val1 output: val1==3 val2==1 val3==1 Can I store same value under different keys?And if possible how can I find the number of appearances efficiently? 回答1: Yes, you can store the same value under different keys. To count the occurrences, I would perhaps maintain a secondary map that maps the

问题 I'm looking to do a lookup that is sort of a hybrid between a join and union. I have a large number of records in my main dataset, so I'm looking to do something that wouldn't be a "brute force" method of a many-to-many matrix. Here is my main dataset, called 'All', which already contains price for each of the products listed. product date price apple 1/1/2011 1.05 apple 1/3/2011 1.02 apple 1/4/2011 1.07 pepper 1/2/2011 0.73 pepper 1/3/2011 0.75 pepper 1/6/2011 0.79 My other data dataset (

问题 I am using the djb2 hash function for c, when I run a name through it I am getting hash numbers in the hundreds of thousands, I would like to get to be able to put this in a hash table using an array of a few thousand or something smaller at least inside a long. I am confused about how to get the function to give me smaller hashes while still having the integrity of the hash. Also I am confused about how to decide on the proper size of array to use for my hash table. Thank you in advance.