cs_hash_set.md

Hash Set (C#)

The HashSet<T> class provides high-performance set operations. A Set is a collection that containers no duplicate elements and whose elements are in no particular order

Characteristics

• A HashSet<T> object's capacity automatically increases as elements are added to the object.
• Based on the model of mathematical sets and provides high-performance set operations similar to accessing the keys of the Dictionary<TKey, TValue> or Hashtable collection.
  • Can be thought of as a Dictionary<TKey, TValue> collection without values.

Sample Code

C#

HashSet<string> dangerousBeasts = new HashSet<string>();
HashSet<string> friendlyBeasts = new HastSet<string>();

dangerousBeasts.Add("Grindylow");
dangerousBeasts.Add("Obscurus");
dangerousBeasts.Add("Erumpent");

friendlyBeasts.Add("Niffler");
friendlyBeasts.Add("Bowtruckle");
friendlyBeasts.Add("Demiguise");

Console.Write("Number of friendly beasts: " + friendlyBeasts.Count);    // Number of friendly beasts: 3
Console.Write("Number of dangerous beasts: " + dangerousBeasts.Count);  // Number of dangerous beasts: 3

HashSet<string> allBeasts = new HashSet<string>();
allBeasts.UnionWith(dangerousBeasts);   // Results in {Grindylow, Obscurus, Erumpent}
allBeasts.UnionWith(friendlyBeasts);    // Results in {Grindylow, Obscurus, Erumpent, Niffler, Bowtruckle, Demiguise}

Cheat Sheet

Description	Code	Remarks
Union	UnionWith (IEnumerable<T>)	Performs a set Union
IntersectWith	IntersectWith (IEnumerable<T>)	Performs mathematical intersection on HashSet<T> and the given collection