.net 集合，用于快速插入/删除

Question

我需要维护一个连接的客户名册，这些客户的寿命很短，并且经常上下波动。由于潜在的客户数量，我需要一个支持快速插入/删除的集合。有什么建议吗？

Answer 1

为此考虑基于哈希的集合，例如HashSet、Dictionary、HashTable，为添加和删除元素提供恒定的时间性能。

来自 .NET Framework 开发人员指南的更多信息：

• Hashtable and Dictionary Collection Types
• HashSet Collection Type

Answer 2

C5 通用集合库

我在 C# 和 C++ 中找到的最佳实现是这些——对于 C#/CLI：

• http://www.itu.dk/research/c5/Release1.1/ITU-TR-2006-76.pdf
• http://www.itu.dk/research/c5/

它经过充分研究，具有可扩展的单元测试，并且自 2 月以来，他们还在 .Net 中实现了通用接口，这使得使用集合变得更加容易。他们出现在 Channel9 上，并且他们对这些集合进行了广泛的性能测试。

如果您无论如何都在使用数据结构，这些研究人员在他们的库中有一个red-black-tree 实现，类似于您启动 Lütz 反射器并查看 System.Data 的内部结构时发现的结果：p。插入复杂度：O(log(n))。

无锁 C++ 集合

那么，如果你可以allow for some C++ interop 并且你绝对需要速度并且希望尽可能少的开销，那么来自 Dmitriy V'jukov 的这些无锁 ADT 可能是世界上最好的，优于英特尔的并发ADT 库。

• http://groups.google.com/group/lock-free

我已经阅读了一些代码，这确实是一个精通这些东西如何组合在一起的人的素质。 VC++ 可以进行本机 C++ 互操作而没有烦人的边界。 http://www.swig.org/ 可以帮助您包装 C++ 接口以在 .Net 中使用，或者您可以通过 P/Invoke 自己完成。

微软的看法

他们编写了教程，this one implementing a rather unpolished skip-list in C#，并讨论了其他类型的数据结构。 （有一个更好的SkipList at CodeProject，它非常精巧并以良好的方式实现了接口。）它们还有一些与.Net 捆绑在一起的数据结构，即HashTable/Dictionary<,> 和HashSet。当然还有“ResizeArray”/List 类型以及堆栈和队列，但它们在搜索时都是“线性”的。

Google 的性能工具

如果您希望加快内存分配的时间，您可以使用 google 的 perf-tools。它们可在 google 代码中找到，它们包含一个 very interesting multi-threaded malloc-implementation (TCMalloc)，它显示出比普通 malloc 更一致的时序。您可以将它与上面的无锁结构一起使用，以真正提高性能。

通过记忆提高响应时间

您还可以在函数上使用 memoization 通过缓存来提高性能，如果您正在使用例如F#。 F# 还允许 C++ 互操作，所以你没问题。

O(k)

也有可能使用在bloom-filters 上完成的研究自己做某事，这允许 O(k) 查找复杂度，其中 k 是一个常数，取决于您已实现的哈希函数的数量.这就是 google 的 BigTable 的实现方式。这些过滤器将为您提供元素，如果它在集合中，或者可能具有非常低的可能性的元素不是您正在寻找的元素（参见维基百科上的图表 - 它接近 P(wrong_key) -> 0.01 作为大小大约有 10000 个元素，但您可以通过实现进一步的哈希函数/减少集合来解决这个问题。

我没有搜索过这个的 .Net 实现，但是由于哈希计算是独立的，你可以使用 MS's performance team's implementation of Tasks to speed that up.

"My" take -- 随机化以达到平均 O(log n)

碰巧我刚刚做了一个涉及数据结构的课程。在本例中，我们使用了 C++，但它很容易转换为 C#。我们构建了三种不同的数据结构；布隆过滤器、跳过列表和random binary search tree。

看最后一段后面的代码和分析。

基于硬件的“集合”

最后，为了让我的回答“完整”，如果你真的需要速度，你可以使用 Routing-tables 或 Content-addressable memory 之类的东西。这允许您在原则上非常快速地 O(1) 获得数据的“哈希”到值查找。

随机二叉搜索树/布隆过滤器 C++ 代码

如果您发现代码中的错误，或者只是关于我如何可以做得更好（或更好地使用模板）的指针，我将非常感谢您的反馈。请注意，布隆过滤器与现实生活中的不同。通常，您不必能够从中删除，然后它比我为允许测试 delete 所做的 hack 更节省空间。

DataStructure.h

#ifndef DATASTRUCTURE_H_
#define DATASTRUCTURE_H_

class DataStructure
{
public:
    DataStructure() {countAdd=0; countDelete=0;countFind=0;}
    virtual ~DataStructure() {}

    void resetCountAdd() {countAdd=0;}
    void resetCountFind() {countFind=0;}
    void resetCountDelete() {countDelete=0;}

    unsigned int getCountAdd(){return countAdd;}
    unsigned int getCountDelete(){return countDelete;}
    unsigned int getCountFind(){return countFind;}

protected:
    unsigned int countAdd;
    unsigned int countDelete;
    unsigned int countFind;
};

#endif /*DATASTRUCTURE_H_*/

Key.h

#ifndef KEY_H_
#define KEY_H_

#include <string>
using namespace std;

const int keyLength = 128;

class Key : public string
{
public:
    Key():string(keyLength, ' ') {}
    Key(const char in[]): string(in){}
    Key(const string& in): string(in){}

    bool operator<(const string& other);
    bool operator>(const string& other);
    bool operator==(const string& other);

    virtual ~Key() {}
};

#endif /*KEY_H_*/

Key.cpp

#include "Key.h"

bool Key::operator<(const string& other)
{
    return compare(other) < 0;
};

bool Key::operator>(const string& other)
{
    return compare(other) > 0;
};

bool Key::operator==(const string& other)
{
    return compare(other) == 0;
}

BloomFilter.h

#ifndef BLOOMFILTER_H_
#define BLOOMFILTER_H_

#include <iostream>
#include <assert.h>
#include <vector>
#include <math.h>
#include "Key.h"
#include "DataStructure.h"

#define LONG_BIT 32
#define bitmask(val) (unsigned long)(1 << (LONG_BIT - (val % LONG_BIT) - 1))

// TODO: Implement RW-locking on the reads/writes to the bitmap.

class BloomFilter : public DataStructure
{
public:
    BloomFilter(){}
    BloomFilter(unsigned long length){init(length);}
    virtual ~BloomFilter(){}

    void init(unsigned long length);
    void dump();

    void add(const Key& key);
    void del(const Key& key);

    /**
     * Returns true if the key IS BELIEVED to exist, false if it absolutely doesn't.
     */
    bool testExist(const Key& key, bool v = false);

private:
    unsigned long hash1(const Key& key);
    unsigned long hash2(const Key& key);
    bool exist(const Key& key);
    void getHashAndIndicies(unsigned long& h1, unsigned long& h2, int& i1, int& i2, const Key& key);
    void getCountIndicies(const int i1, const unsigned long h1,
        const int i2, const unsigned long h2, int& i1_c, int& i2_c);

    vector<unsigned long> m_tickBook;
    vector<unsigned int> m_useCounts;
    unsigned long m_length; // number of bits in the bloom filter
    unsigned long m_pockets; //the number of pockets

    static const unsigned long m_pocketSize; //bits in each pocket
};

#endif /*BLOOMFILTER_H_*/

BloomFilter.cpp

#include "BloomFilter.h"

const unsigned long BloomFilter::m_pocketSize = LONG_BIT;

void BloomFilter::init(unsigned long length)
{
    //m_length = length;
    m_length = (unsigned long)((2.0*length)/log(2))+1;
    m_pockets = (unsigned long)(ceil(double(m_length)/m_pocketSize));
    m_tickBook.resize(m_pockets);

    // my own (allocate nr bits possible to store in the other vector)
    m_useCounts.resize(m_pockets * m_pocketSize);

    unsigned long i; for(i=0; i< m_pockets; i++) m_tickBook[i] = 0;
    for (i = 0; i < m_useCounts.size(); i++) m_useCounts[i] = 0; // my own
}

unsigned long BloomFilter::hash1(const Key& key)
{
    unsigned long hash = 5381;
    unsigned int i=0; for (i=0; i< key.length(); i++){
        hash = ((hash << 5) + hash) + key.c_str()[i]; /* hash * 33 + c */
    }

    double d_hash = (double) hash;

    d_hash *= (0.5*(sqrt(5)-1));
    d_hash -= floor(d_hash);
    d_hash *= (double)m_length;

    return (unsigned long)floor(d_hash);
}

unsigned long BloomFilter::hash2(const Key& key)
{
    unsigned long hash = 0;
    unsigned int i=0; for (i=0; i< key.length(); i++){
        hash = key.c_str()[i] + (hash << 6) + (hash << 16) - hash;
    }
    double d_hash = (double) hash;

    d_hash *= (0.5*(sqrt(5)-1));
    d_hash -= floor(d_hash);
    d_hash *= (double)m_length;

    return (unsigned long)floor(d_hash);
}

bool BloomFilter::testExist(const Key& key, bool v){
    if(exist(key)) {
        if(v) cout<<"Key "<< key<<" is in the set"<<endl;
        return true;
    }else {
        if(v) cout<<"Key "<< key<<" is not in the set"<<endl;
        return false;
    }
}

void BloomFilter::dump()
{
    cout<<m_pockets<<" Pockets: ";

    // I changed u to %p because I wanted it printed in hex.
    unsigned long i; for(i=0; i< m_pockets; i++) printf("%p ", (void*)m_tickBook[i]);
    cout<<endl;
}

void BloomFilter::add(const Key& key)
{
    unsigned long h1, h2;
    int i1, i2;
    int i1_c, i2_c;

    // tested!

    getHashAndIndicies(h1, h2, i1, i2, key);
    getCountIndicies(i1, h1, i2, h2, i1_c, i2_c);

    m_tickBook[i1] = m_tickBook[i1] | bitmask(h1);
    m_tickBook[i2] = m_tickBook[i2] | bitmask(h2);

    m_useCounts[i1_c] = m_useCounts[i1_c] + 1;
    m_useCounts[i2_c] = m_useCounts[i2_c] + 1;

    countAdd++;
}

void BloomFilter::del(const Key& key)
{
    unsigned long h1, h2;
    int i1, i2;
    int i1_c, i2_c;

    if (!exist(key)) throw "You can't delete keys which are not in the bloom filter!";

    // First we need the indicies into m_tickBook and the
    // hashes.
    getHashAndIndicies(h1, h2, i1, i2, key);

    // The index of the counter is the index into the bitvector
    // times the number of bits per vector item plus the offset into
    // that same vector item.
    getCountIndicies(i1, h1, i2, h2, i1_c, i2_c);

    // We need to update the value in the bitvector in order to
    // delete the key.
    m_useCounts[i1_c] = (m_useCounts[i1_c] == 1 ? 0 : m_useCounts[i1_c] - 1);
    m_useCounts[i2_c] = (m_useCounts[i2_c] == 1 ? 0 : m_useCounts[i2_c] - 1);

    // Now, if we depleted the count for a specific bit, then set it to
    // zero, by anding the complete unsigned long with the notted bitmask
    // of the hash value
    if (m_useCounts[i1_c] == 0)
        m_tickBook[i1] = m_tickBook[i1] & ~(bitmask(h1));
    if (m_useCounts[i2_c] == 0)
        m_tickBook[i2] = m_tickBook[i2] & ~(bitmask(h2));

    countDelete++;
}

bool BloomFilter::exist(const Key& key)
{
    unsigned long h1, h2;
    int i1, i2;

    countFind++;

    getHashAndIndicies(h1, h2, i1, i2, key);

    return  ((m_tickBook[i1] & bitmask(h1)) > 0) &&
            ((m_tickBook[i2] & bitmask(h2)) > 0);
}

/*
 * Gets the values of the indicies for two hashes and places them in
 * the passed parameters. The index is into m_tickBook.
 */
void BloomFilter::getHashAndIndicies(unsigned long& h1, unsigned long& h2, int& i1,
    int& i2, const Key& key)
{
    h1 = hash1(key);
    h2 = hash2(key);
    i1 = (int) h1/m_pocketSize;
    i2 = (int) h2/m_pocketSize;
}

/*
 * Gets the values of the indicies into the count vector, which keeps
 * track of how many times a specific bit-position has been used.
 */
void BloomFilter::getCountIndicies(const int i1, const unsigned long h1,
    const int i2, const unsigned long h2, int& i1_c, int& i2_c)
{
    i1_c = i1*m_pocketSize + h1%m_pocketSize;
    i2_c = i2*m_pocketSize + h2%m_pocketSize;
}

** RBST.h **

#ifndef RBST_H_
#define RBST_H_

#include <iostream>
#include <assert.h>
#include <vector>
#include <math.h>
#include "Key.h"
#include "DataStructure.h"

#define BUG(str) printf("%s:%d FAILED SIZE INVARIANT: %s\n", __FILE__, __LINE__, str);

using namespace std;

class RBSTNode;
class RBSTNode: public Key
{
public:
    RBSTNode(const Key& key):Key(key)
    {
        m_left =NULL;
        m_right = NULL;
        m_size = 1U; // the size of one node is 1.
    }
    virtual ~RBSTNode(){}

    string setKey(const Key& key){return Key(key);}

    RBSTNode* left(){return m_left; }
    RBSTNode* right(){return m_right;}

    RBSTNode* setLeft(RBSTNode* left) { m_left = left; return this; }
    RBSTNode* setRight(RBSTNode* right) { m_right =right; return this; }

#ifdef DEBUG
    ostream& print(ostream& out)
    {
        out << "Key(" << *this << ", m_size: " << m_size << ")";
        return out;
    }
#endif

    unsigned int size() { return m_size; }

    void setSize(unsigned int val)
    {
#ifdef DEBUG
        this->print(cout);
        cout << "::setSize(" << val << ") called." << endl;
#endif

        if (val == 0) throw "Cannot set the size below 1, then just delete this node.";
        m_size = val;
    }

    void incSize() {
#ifdef DEBUG
        this->print(cout);
        cout << "::incSize() called" << endl;
#endif

        m_size++;
    }

    void decrSize()
    {
#ifdef DEBUG
        this->print(cout);
        cout << "::decrSize() called" << endl;
#endif

        if (m_size == 1) throw "Cannot decrement size below 1, then just delete this node.";
        m_size--;
    }

#ifdef DEBUG
    unsigned int size(RBSTNode* x);
#endif

private:
    RBSTNode(){}
    RBSTNode* m_left;
    RBSTNode* m_right;
    unsigned int m_size;
};

class RBST : public DataStructure
{
public:
    RBST() {
        m_size = 0;
        m_head = NULL;
        srand(time(0));
    };

    virtual ~RBST() {};

    /**
     * Tries to add key into the tree and will return
     *      true  for a new item added
     *      false if the key already is in the tree.
     *
     * Will also have the side-effect of printing to the console if v=true.
     */
    bool add(const Key& key, bool v=false);

    /**
     * Same semantics as other add function, but takes a string,
     * but diff name, because that'll cause an ambiguity because of inheritance.
     */
    bool addString(const string& key);

    /**
     * Deletes a key from the tree if that key is in the tree.
     * Will return
     *      true  for success and
     *      false for failure.
     *
     * Will also have the side-effect of printing to the console if v=true.
     */
    bool del(const Key& key, bool v=false);

    /**
     * Tries to find the key in the tree and will return
     *      true if the key is in the tree and
     *      false if the key is not.
     *
     * Will also have the side-effect of printing to the console if v=true.
     */
    bool find(const Key& key, bool v = false);

    unsigned int count() { return m_size; }

#ifdef DEBUG
    int dump(char sep = ' ');
    int dump(RBSTNode* target, char sep);
    unsigned int size(RBSTNode* x);
#endif

private:
    RBSTNode* randomAdd(RBSTNode* target, const Key& key);
    RBSTNode* addRoot(RBSTNode* target, const Key& key);
    RBSTNode* rightRotate(RBSTNode* target);
    RBSTNode* leftRotate(RBSTNode* target);

    RBSTNode* del(RBSTNode* target, const Key& key);
    RBSTNode* join(RBSTNode* left, RBSTNode* right);

    RBSTNode* find(RBSTNode* target, const Key& key);

    RBSTNode* m_head;
    unsigned int m_size;
};

#endif /*RBST_H_*/

** RBST.cpp **

#include "RBST.h"

bool RBST::add(const Key& key, bool v){
    unsigned int oldSize = m_size;
    m_head = randomAdd(m_head, key);
    if (m_size > oldSize){
        if(v) cout<<"Node "<<key<< " is added into the tree."<<endl;
        return true;
    }else {
        if(v) cout<<"Node "<<key<< " is already in the tree."<<endl;
        return false;
    }
    if(v) cout<<endl;
};

bool RBST::addString(const string& key) {
    return add(Key(key), false);
}

bool RBST::del(const Key& key, bool v){
    unsigned oldSize= m_size;
    m_head = del(m_head, key);
    if (m_size < oldSize) {
        if(v) cout<<"Node "<<key<< " is deleted from the tree."<<endl;
        return true;
    }
    else {
        if(v) cout<< "Node "<<key<< " is not in the tree."<<endl;
        return false;
    }
};

bool RBST::find(const Key& key, bool v){
    RBSTNode* ret = find(m_head, key);
    if (ret == NULL){
        if(v) cout<< "Node "<<key<< " is not in the tree."<<endl;
        return false;
    }else {
        if(v) cout<<"Node "<<key<< " is in the tree."<<endl;
        return true;
    }
};

#ifdef DEBUG
int RBST::dump(char sep){
    int ret = dump(m_head, sep);
    cout<<"SIZE: " <<ret<<endl;
    return ret;
};

int RBST::dump(RBSTNode* target, char sep){
    if (target == NULL) return 0;
    int ret = dump(target->left(), sep);
    cout<< *target<<sep;
    ret ++;
    ret += dump(target->right(), sep);
    return ret;
};
#endif

/**
 * Rotates the tree around target, so that target's left
 * is the new root of the tree/subtree and updates the subtree sizes.
 *
 *(target)  b               (l) a
 *         / \      right      / \
 *        a   ?     ---->     ?   b
 *       / \                     / \
 *      ?   x                   x   ?
 *
 */
RBSTNode* RBST::rightRotate(RBSTNode* target) // private
{
    if (target == NULL) throw "Invariant failure, target is null"; // Note: may be removed once tested.
    if (target->left() == NULL) throw "You cannot rotate right around a target whose left node is NULL!";

#ifdef DEBUG
    cout    <<"Right-rotating b-node ";
    target->print(cout);
    cout    << " for a-node ";
    target->left()->print(cout);
    cout    << "." << endl;
#endif

    RBSTNode* l = target->left();
    int as0 = l->size();

    // re-order the sizes
    l->setSize( l->size() + (target->right() == NULL ? 0 : target->right()->size()) + 1); // a.size += b.right.size + 1; where b.right may be null.
    target->setSize( target->size() -as0 + (l->right() == NULL ? 0 : l->right()->size()) ); // b.size += -a_0_size + x.size where x may be null.

    // swap b's left (for a)
    target->setLeft(l->right());

    // and a's right (for b's left)
    l->setRight(target);

#ifdef DEBUG
    cout    << "A-node size: " << l->size() << ", b-node size: " << target->size() << "." << endl;
#endif

    // return the new root, a.
    return l;
};

/**
 * Like rightRotate, but the other way. See docs for rightRotate(RBSTNode*)
 */
RBSTNode* RBST::leftRotate(RBSTNode* target)
{
    if (target == NULL) throw "Invariant failure, target is null";
    if (target->right() == NULL) throw "You cannot rotate left around a target whose right node is NULL!";

#ifdef DEBUG
    cout    <<"Left-rotating a-node ";
    target->print(cout);
    cout    << " for b-node ";
    target->right()->print(cout);
    cout    << "." << endl;
#endif

    RBSTNode* r = target->right();
    int bs0 = r->size();

    // re-roder the sizes
    r->setSize(r->size() + (target->left() == NULL ? 0 : target->left()->size()) + 1);
    target->setSize(target->size() -bs0 + (r->left() == NULL ? 0 : r->left()->size()));

    // swap a's right (for b's left)
    target->setRight(r->left());

    // swap b's left (for a)
    r->setLeft(target);

#ifdef DEBUG
    cout    << "Left-rotation done: a-node size: " << target->size() << ", b-node size: " << r->size() << "." << endl;
#endif

    return r;
};

//
/**
 * Adds a key to the tree and returns the new root of the tree.
 * If the key already exists doesn't add anything.
 * Increments m_size if the key didn't already exist and hence was added.
 *
 * This function is not called from public methods, it's a helper function.
 */
RBSTNode* RBST::addRoot(RBSTNode* target, const Key& key)
{
    countAdd++;

    if (target == NULL) return new RBSTNode(key);

#ifdef DEBUG
    cout << "addRoot(";
    cout.flush();
    target->print(cout) << "," << key << ") called." << endl;
#endif

    if (*target < key)
    {
        target->setRight( addRoot(target->right(), key) );
        target->incSize(); // Should I?
        RBSTNode* res = leftRotate(target);
#ifdef DEBUG
        if (target->size() != size(target))
            BUG("in addRoot 1");
#endif
        return res;
    }

    target->setLeft( addRoot(target->left(), key) );
    target->incSize(); // Should I?
    RBSTNode* res = rightRotate(target);
#ifdef DEBUG
    if (target->size() != size(target))
        BUG("in addRoot 2");
#endif
    return res;
};

/**
 * This function is called from the public add(key) function,
 * and returns the new root node.
 */
RBSTNode* RBST::randomAdd(RBSTNode* target, const Key& key)
{
    countAdd++;

    if (target == NULL)
    {
        m_size++;
        return new RBSTNode(key);
    }

#ifdef DEBUG
    cout << "randomAdd(";
    target->print(cout) << ", \"" << key << "\") called." << endl;
#endif

    int r = (rand() % target->size()) + 1;

    // here is where we add the target as root!
    if (r == 1)
    {
        m_size++;   // TODO: Need to lock.
        return addRoot(target, key);
    }

#ifdef DEBUG
    printf("randomAdd recursion part, ");
#endif

    // otherwise, continue recursing!
    if (*target <= key)
    {
#ifdef DEBUG
    printf("target <= key\n");
#endif
        target->setRight( randomAdd(target->right(), key) );
        target->incSize(); // TODO: Need to lock.
#ifdef DEBUG
        if (target->right()->size() != size(target->right()))
            BUG("in randomAdd 1");
#endif
    }
    else
    {
#ifdef DEBUG
    printf("target > key\n");
#endif
        target->setLeft( randomAdd(target->left(), key) );
        target->incSize(); // TODO: Need to lock.
#ifdef DEBUG
        if (target->left()->size() != size(target->left()))
            BUG("in randomAdd 2");
#endif
    }

#ifdef DEBUG
    printf("randomAdd return part\n");
#endif

    m_size++;       // TODO: Need to lock.
    return target;
};

/////////////////////////////////////////////////////////////
/////////////////////  DEL FUNCTIONS ////////////////////////
/////////////////////////////////////////////////////////////

/**
 * Deletes a node with the passed key.
 * Returns the root node.
 * Decrements m_size if something was deleted.
 */
RBSTNode* RBST::del(RBSTNode* target, const Key& key)
{
    countDelete++;

    if (target == NULL) return NULL;

#ifdef DEBUG
    cout << "del(";
    target->print(cout) << ", \"" << key << "\") called." << endl;
#endif

    RBSTNode* ret = NULL;

    // found the node to delete
    if (*target == key)
    {
        ret = join(target->left(), target->right());

        m_size--;
        delete target;

        return ret; // return the newly built joined subtree!
    }

    // store a temporary size before recursive deletion.
    unsigned int size = m_size;

    if (*target < key)  target->setRight( del(target->right(), key) );
    else                target->setLeft( del(target->left(), key) );

    // if the previous recursion changed the size, we need to decrement the size of this target too.
    if (m_size < size) target->decrSize();

#ifdef DEBUG
    if (RBST::size(target) != target->size())
        BUG("in del");
#endif

    return target;
};

/**
 * Joins the two subtrees represented by left and right
 * by randomly choosing which to make the root, weighted on the
 * size of the sub-tree.
 */
RBSTNode* RBST::join(RBSTNode* left, RBSTNode* right)
{
    if (left == NULL) return right;
    if (right == NULL) return left;

#ifdef DEBUG
    cout << "join(";
    left->print(cout);
    cout << ",";
    right->print(cout) << ") called." << endl;
#endif

    // Find the chance that we use the left tree, based on its size over the total tree size.
    // 3 s.d. randomness :-p e.g. 60.3% chance.
    bool useLeft = ((rand()%1000) < (signed)((float)left->size()/(float)(left->size() + right->size()) * 1000.0));

    RBSTNode* subtree = NULL;

    if (useLeft)
    {
        subtree = join(left->right(), right);

        left->setRight(subtree)
            ->setSize((left->left() == NULL ? 0 : left->left()->size())
                        + subtree->size() + 1 );

#ifdef DEBUG
        if (size(left) != left->size())
            BUG("in join 1");
#endif

        return left;
    }

    subtree = join(right->left(), left);

    right->setLeft(subtree)
         ->setSize((right->right() == NULL ? 0 : right->right()->size())
                    + subtree->size() + 1);

#ifdef DEBUG
    if (size(right) != right->size())
        BUG("in join 2");
#endif

    return right;
};

/////////////////////////////////////////////////////////////
/////////////////////  FIND FUNCTIONS ///////////////////////
/////////////////////////////////////////////////////////////

/**
 * Tries to find the key in the tree starting
 * search from target.
 *
 * Returns NULL if it was not found.
 */
RBSTNode* RBST::find(RBSTNode* target, const Key& key)
{
    countFind++; // Could use private method only counting the first call.
    if (target == NULL) return NULL; // not found.
    if (*target == key) return target; // found (does string override ==?)
    if (*target < key) return find(target->right(), key); // search for gt to the right.
    return find(target->left(), key); // search for lt to the left.
};

#ifdef DEBUG

unsigned int RBST::size(RBSTNode* x)
{
    if (x == NULL) return 0;
    return 1 + size(x->left()) + size(x->right());
}

#endif

我将再次保存 SkipList，因为已经可以从链接中找到好的 SkipList 实现，而且我的版本并没有太大的不同。

测试文件生成的图表如下：

图表显示为 BloomFilter、RBST 和 SkipList 添加新项目所用的时间。 graph http://haf.se/content/dl/addtimer.png

图表显示为 BloomFilter、RBST 和 SkipList 查找项目所用的时间 graph http://haf.se/content/dl/findtimer.png

图表显示删除 BloomFilter、RBST 和 SkipList 项所用的时间 graph http://haf.se/content/dl/deltimer.png

如您所见，随机二叉搜索树比 SkipList 好很多。布隆过滤器不辜负它的 O(k)。

Answer 3

好吧，你需要查询多少？链接列表具有快速插入/删除（在任何位置），但不如（例如）字典/排序列表那么快搜索。或者，每个中都有一个位/值对的直接列表 - 即“仍然具有价值”。只需在追加之前重新使用 逻辑上 空单元格。删除只是清除单元格。

对于引用类型，这里可以使用“null”。对于值类型，Nullable<T>。

Answer 4

您可以使用 Hashtable 或强类型 Dictionary。客户端类可能会覆盖 GetHashCode 以提供更快的哈希码生成，或者如果使用 Hashtable，您可以选择使用 IHashCodeProvider。

Answer 5

您需要如何找到客户？元组/字典是否必要？您很有可能在 Jeffrey Richter 的 Power Collections 库中找到解决问题的方法，该库包含列表、树和大多数您能想到的数据结构。

Answer 6

Channel9 对 Peter Sestoft 的采访给我留下了深刻的印象：

channel9.msdn.com/shows/Going+Deep/Peter-Sestoft-C5-Generic-Collection-Library-for-C-and-CLI/

他是哥本哈根 IT 大学的教授，曾帮助创建 C5 通用集合库：

www.itu.dk/research/c5/

这可能是矫枉过正，或者它可能只是你正在寻找的快速收集......

第，

-迈克