我需要一个等效std::multimap<K, V, Comp, Alloc>于 C-sharp 中的 c++ 的东西。它是否存在于标准库中？
Roger Schildmeijer
问问题
44102 次
6 回答
53
因为快过圣诞节了：）
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// Algorithmia is (c) 2008 Solutions Design. All rights reserved.
// http://www.sd.nl
//////////////////////////////////////////////////////////////////////
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// Copyright (c) 2008 Solutions Design. All rights reserved.
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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;
}
}
}
于 2008-12-19T10:32:32.217 回答
20
ILookup可能对你来说已经足够好了——但不幸的是没有公开的实现。据我所知，您基本上必须通过Enumerable.ToLookup 。这意味着它是一种“构建一次”的地图 - 您以后无法添加。但是，如果这就是您所需要的，那么能够只使用内置的东西就很方便了。
于 2008-12-19T10:46:20.443 回答
11
在 .NET 3.5 中，有一个ILookup<,>代表这一点。常规实现 ( Lookup<,>) 是不可变的，但我EditableLookup<,>在MiscUtil中有一个应该可以很好地完成这项工作。
于 2008-12-19T11:09:27.197 回答
2
于 2010-04-06T11:53:59.183 回答
2
你可以找到 ac# multimap collection @ http://code.google.com/p/self-balancing-avl-tree/。它基于代码中也包含的自平衡 avl 树。
于 2012-07-25T00:03:29.563 回答
0
BMultiMap<K,V>如果您的收藏整体很大，请考虑使用。与 相比，它节省了大量内存Dictionary<K,List<V>>，尤其是在与每个键关联的值的数量通常很小的情况下。
于 2014-01-25T18:58:00.303 回答