hashset

问题 According to JavaDoc API a HashSet is just a wrapper around a HashMap. Therefore can there ever be any performance benefit to using a HashSet over a HashMap. Ever? Ever? Or is just to have a different API which suits other cases? 回答1: No, there's no "performance" benefit; there's just the benefit that comes from using the right API for the right problem...which is considerable. 回答2: Not Really there are no Performance benefits, They both serves for the different purpose. About Hashset in API

问题 I'm basing this on performance characteristics I've recently found out about Dictionary , so I'm using Dictionary<type, bool> where the bool is ignored but supposedly I could use HashSet instead. For example: Dictionary<bounds, bool> overlap; class bounds { public float top_left_x, top_left_y, width, height; public bool equal(bounds other) { return upper_left_x + width > other.upper_left_x && upper_left_x < other.upper_left_x + other.width && upper_left_y + height > other.upper_left_y &&

问题 Reading HashSet on MSDN, it says with HashSet<T> , if T implements IEquatable<T> then the HashSet uses this for IEqualityComparer<T>.Default . So, let the class Person: public class Person : IEquality<Person> { private string pName; public Person(string name){ pName=name; } public string Name { get { return pName; } set { if (pName.Equals(value, StringComparison.InvariantCultureIgnoreCase)) { return; } pName = value; } } public bool Equals(Person other) { if(other==null){return false;} return

问题 C# XNA Xbox, in this case optional parameters are not optional Thanks to help from the above question optional parameters are now working, or at least appear as if they should work. However I'm now stuck on HashSets and Tuples, that don't appear to be available either. I could write my own version of both classes. Tuple from scratch and HashSet using a Dictonary (possibly). However I'd rather keep to using the standard ones. If these classes exist in the PC verstion of the library, then can I

问题 I learned that HashSet implements the IEnumerable interface. Thus, it is possible to implicitly cast a HashSet object into IEnumerable : HashSet<T> foo = new HashSet<T>(); IEnumerable<T> foo2 = foo; // Implicit cast, everything fine. This works for nested generic types, too: HashSet<HashSet<T>> dong = new HashSet<HashSet<T>>(); IEnumerable<IEnumerable<T>> dong2 = dong; // Implicit cast, everything fine. At least that's what I thought. But if I make a Dictionary , I run into a problem:

问题 I am looking if there is a pre-existing .Net 'Hash-Set type' implementation suitable to atomizing a general type T. We have a large number of identical objects coming in for serialized sources that need to be atomized to conserve memory. A Dictionary<T,T> with the value == key works perfectly, however the objects in these collections can run into the millions across the app, and so it seem very wasteful to store 2 references to every object. HashSet cannot be used as it only has Contains,

问题 I'm looking for a suggestion. I have a Person class with String firstName and String lastName When i'm tying to insert the list values with the same String like : set.add(new Person("firstName","lastName")) set.add(new Person("firstName","lastName")) The set doesn`t filter the objects and they still getting in the set. There is any suggestion to create set list without overriding the equales and hashcode functions? Maybe with guava or some groovy list? Thanks, Or. 回答1: You can create a

问题 I'm creating my own HashSet that works as the standard HashSet, using a Dictionary. I'm doing this because C# for XNA XBox doesn't support HashSets. This code is based on code from an example I found. I've edited the example to fix some of the problems but it still won't compile. public class HashSet2<T> : ICollection<T> { private Dictionary<T, Int16> dict; // code has been edited out of this example // see further on in the question for the full class public IEnumerator<T> GetEnumerator() {

问题 I do not understand why hastable's rehash complexity may be quadratic in worst case at : http://www.cplusplus.com/reference/unordered_set/unordered_multiset/reserve/ Any help would be appreciated ! Thanks 回答1: Just some basics: Hash collisions is when two or more elements take on the same hash. This can cause worst-case O(n) operations. I won't really go into this much further, since one can find many explanations of this. Basically all the elements can have the same hash, thus you'll have

问题 I've got a list of bookmarks. Each bookmark has a list of keywords (stored as a HashSet). I also have a set of all possible keywords ("universe"). I want to find the keyword that appears in the most bookmarks. I have 1356 bookmarks with a combined total of 698,539 keywords, with 187,358 unique. If I iterate through every keyword in the universe and count the number of bookmarks it appears in, I'm doing 254,057,448 checks. This takes 35 seconds on my machine. The algorithm is pretty simple: