《学习笔记》System.Collections.Generic 命名空间 HashSet<T>

挺方便的一个类，提供了对数据集的批量操作，尤其是合并与删除 对于解决一些特殊问题还是挺有帮助的。 

Methods
Add	CopyTo
Clear
ExceptWith	Removes all elements in the specified collection from the current HashSet < T > object	示例见下：
IntersectWith	Modifies the current HashSet < T > object to contain only elements that are present in that object and in the specified collection.	与ExceptWith 用法相似。
IsProperSubsetOf	Determines whether a HashSet < T > object is a proper subset of the specified collection.
IsProperSupersetOf	Determines whether a HashSet < T > object is a proper superset of the specified collection
Remove	Removes the specified element from a HashSet < T > object.
RemoveWhere	Removes all elements that match the conditions defined by the specified predicate from a HashSet < T > collection.
UnionWith	Modifies the current HashSet < T > object to contain all elements that are present in both itself and in the specified collection.	示例见下：
TrimExcess	Sets the capacity of a HashSet < T > object to the actual number of elements it contains, rounded up to a nearby, implementation-specific value.

 

 

 

// HashSet  Example


static void Main()
{
    HashSet<int> lowNumbers = new HashSet<int>();
    HashSet<int> highNumbers = new HashSet<int>();

    for (int i = 0; i < 6; i++)
    {
        lowNumbers.Add(i);
    }

    for (int i = 3; i < 10; i++)
    {
        highNumbers.Add(i);
    }

    Console.Write("lowNumbers contains {0} elements: ", lowNumbers.Count);
    DisplaySet(lowNumbers);

    Console.Write("highNumbers contains {0} elements: ", highNumbers.Count);
    DisplaySet(highNumbers);

    Console.WriteLine("highNumbers ExceptWith lowNumbers...");
    highNumbers.ExceptWith(lowNumbers);

    Console.Write("highNumbers contains {0} elements: ", highNumbers.Count);
    DisplaySet(highNumbers);



}
/* This example provides output similar to the following:
 * lowNumbers contains 6 elements: { 0 1 2 3 4 5 }
 * highNumbers contains 7 elements: { 3 4 5 6 7 8 9 }
 * highNumbers ExceptWith lowNumbers...
 * highNumbers contains 4 elements: { 6 7 8 9 }
 */

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        HashSet<int> evenNumbers = new HashSet<int>();
        HashSet<int> oddNumbers = new HashSet<int>();

        for (int i = 0; i < 5; i++)
        {
            // Populate numbers with just even numbers.
            evenNumbers.Add(i * 2);

            // Populate oddNumbers with just odd numbers.
            oddNumbers.Add((i * 2) + 1);
        }

        Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count);
        DisplaySet(evenNumbers);

        Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count);
        DisplaySet(oddNumbers);

        // Create a new HashSet populated with even numbers.
        HashSet<int> numbers = new HashSet<int>(evenNumbers);
        Console.WriteLine("numbers UnionWith oddNumbers...");
        numbers.UnionWith(oddNumbers);

        Console.Write("numbers contains {0} elements: ", numbers.Count);
        DisplaySet(numbers);

    }

    private static void DisplaySet(HashSet<int> set)
    {
        Console.Write("{");
        foreach (int i in set)
        {
            Console.Write(" {0}", i);
        }
        Console.WriteLine(" }");
    }
}
/* This example produces output similar to the following:
 * evenNumbers contains 5 elements: { 0 2 4 6 8 }
 * oddNumbers contains 5 elements: { 1 3 5 7 9 }
 * numbers UnionWith oddNumbers...
 * numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }
 */