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

最新推荐文章于 2024-05-25 09:54:07 发布

转载最新推荐文章于 2024-05-25 09:54:07 发布 · 156 阅读

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原文链接：http://www.cnblogs.com/08shiyan/archive/2010/10/26/1861469.html

本文详细介绍了.NET中HashSet<T>类的各种操作方法，包括添加、删除元素，集合间的并集、交集、差集运算等，并通过具体示例展示了如何使用这些方法来高效地处理数据集。

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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.

ExceptWith

// 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 }
*/

UnionWith

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 }
*/

转载于:https://www.cnblogs.com/08shiyan/archive/2010/10/26/1861469.html