我需要在C-sharp中与C++的std::multimap<K, V, Comp, Alloc>
等效。它存在于标准库中吗?multimap
multimap
回答
因为它几乎圣诞节:)
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// Algorithmia is (c) 2008 Solutions Design. All rights reserved.
// http://www.sd.nl
//////////////////////////////////////////////////////////////////////
// COPYRIGHTS:
// Copyright (c) 2008 Solutions Design. All rights reserved.
//
// The Algorithmia library sourcecode and its accompanying tools, tests and support code
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// conditions and the following disclaimer in the documentation and/or other materials
// provided with the distribution.
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// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SOLUTIONS DESIGN OR CONTRIBUTORS BE LIABLE FOR
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// Contributers to the code:
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//////////////////////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using SD.Tools.Algorithmia.UtilityClasses;
namespace SD.Tools.Algorithmia.GeneralDataStructures
{
/// <summary>
/// Extension to the normal Dictionary. This class can store more than one value for every key. It keeps a HashSet for every Key value.
/// Calling Add with the same Key and multiple values will store each value under the same Key in the Dictionary. Obtaining the values
/// for a Key will return the HashSet with the Values of the Key.
/// </summary>
/// <typeparam name="TKey">The type of the key.</typeparam>
/// <typeparam name="TValue">The type of the value.</typeparam>
public class MultiValueDictionary<TKey, TValue> : Dictionary<TKey, HashSet<TValue>>
{
/// <summary>
/// Initializes a new instance of the <see cref="MultiValueDictionary<TKey, TValue>"/> class.
/// </summary>
public MultiValueDictionary()
: base()
{
}
/// <summary>
/// Adds the specified value under the specified key
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
public void Add(TKey key, TValue value)
{
ArgumentVerifier.CantBeNull(key, "key");
HashSet<TValue> container = null;
if(!this.TryGetValue(key, out container))
{
container = new HashSet<TValue>();
base.Add(key, container);
}
container.Add(value);
}
/// <summary>
/// Determines whether this dictionary contains the specified value for the specified key
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
/// <returns>true if the value is stored for the specified key in this dictionary, false otherwise</returns>
public bool ContainsValue(TKey key, TValue value)
{
ArgumentVerifier.CantBeNull(key, "key");
bool toReturn = false;
HashSet<TValue> values = null;
if(this.TryGetValue(key, out values))
{
toReturn = values.Contains(value);
}
return toReturn;
}
/// <summary>
/// Removes the specified value for the specified key. It will leave the key in the dictionary.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
public void Remove(TKey key, TValue value)
{
ArgumentVerifier.CantBeNull(key, "key");
HashSet<TValue> container = null;
if(this.TryGetValue(key, out container))
{
container.Remove(value);
if(container.Count <= 0)
{
this.Remove(key);
}
}
}
/// <summary>
/// Merges the specified multivaluedictionary into this instance.
/// </summary>
/// <param name="toMergeWith">To merge with.</param>
public void Merge(MultiValueDictionary<TKey, TValue> toMergeWith)
{
if(toMergeWith==null)
{
return;
}
foreach(KeyValuePair<TKey, HashSet<TValue>> pair in toMergeWith)
{
foreach(TValue value in pair.Value)
{
this.Add(pair.Key, value);
}
}
}
/// <summary>
/// Gets the values for the key specified. This method is useful if you want to avoid an exception for key value retrieval and you can't use TryGetValue
/// (e.g. in lambdas)
/// </summary>
/// <param name="key">The key.</param>
/// <param name="returnEmptySet">if set to true and the key isn't found, an empty hashset is returned, otherwise, if the key isn't found, null is returned</param>
/// <returns>
/// This method will return null (or an empty set if returnEmptySet is true) if the key wasn't found, or
/// the values if key was found.
/// </returns>
public HashSet<TValue> GetValues(TKey key, bool returnEmptySet)
{
HashSet<TValue> toReturn = null;
if(!base.TryGetValue(key, out toReturn) && returnEmptySet)
{
toReturn = new HashSet<TValue>();
}
return toReturn;
}
}
}
编辑:我misspoke - 我原本以为这打破了LSP(它*可能*) - 但我认为它没关系,因为它没有隐藏任何基类方法,它们仍应按预期工作。向下投票恢复:) – mhand 2017-12-01 20:48:15
ILookup可能是你不够好 - 但遗憾的是没有公开的实现。就我所知,你基本上必须通过Enumerable.ToLookup。这意味着它是一种“构建一次”的地图 - 你以后不能添加。但是,如果这就是你所需要的,那么只需使用内置的东西就可以方便使用。
在.NET 3.5中,有一个代表这个的ILookup<,>
。常规实施(Lookup<,>
)是不可变的,但我有一个EditableLookup<,>
在MiscUtil应该很好地做这项工作。
方便,但我没有看到许可证信息,这意味着它不是真正可用的,因为:/ – 2018-03-01 21:51:35
你可以找到c#multimap collection @http://code.google.com/p/self-balancing-avl-tree/。它基于代码中包含的自平衡avl树。
考虑使用BMultiMap<K,V>
如果您的收藏整体很大。与Dictionary<K,List<V>>
相比,它可以节省大量的内存,特别是如果与每个密钥关联的值的数量通常很少。
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大部分时间在正常词典中使用列表已足够 – Casebash 2010-06-15 05:58:30