跳跃表SkipList(简单的C++实现)_c++ skiplist

不懂跳跃表的请直接百度
直接上实现

#include <iostream>
#include <string.h>
#include <ctime>

using namespace std;

template<typename T>
struct SkipNode {
    inline static constexpr int Rate=3;
    inline static constexpr int MaxHeight=8;
    inline static constexpr intmax_t Inf= INT_MAX;
    inline static SkipNode<T>* update[MaxHeight];

    intmax_t key;
    T val;
    SkipNode<T> *pre[MaxHeight], *nex[MaxHeight];

    SkipNode<T>(intmax_t k=Inf,const T& v = {})
        : key(k), val(v)
    {
        init_pos(nullptr);
    }

    auto init_pos(SkipNode<T>* ptr=nullptr)
    {
        for (int h=0; h<MaxHeight; ++h) {
            pre[h]=nex[h]=ptr;
        }
        return this;
    }

    SkipNode<T>* escape()
    {
        for(int h=0; h<MaxHeight; ++h) {
            auto *p=pre[h], *x=nex[h];
            pre[h]=nex[h]=nullptr;
            if(p)p->nex[h]=x;
            if(x)x->pre[h]=p;
        }
        return this;
    }

    intmax_t upper_bound(intmax_t key__, SkipNode<T> *(&update__)[MaxHeight]=update)
    {
        memset(update__,0,sizeof(update__));
        auto *p = this;
        for(int h=MaxHeight-1; h>=0; --h) {
            while(p->nex[h] && p->nex[h]!=this && p->nex[h]->key > key__) p=p->nex[h];
            update__[h]=p;
        }
        return p->nex[0] ? p->nex[0]->key : Inf;
    }

    void into(SkipNode<T> *(&update__)[MaxHeight]=update)
    {
        this->init_pos(nullptr);
        for(int h=0; h<MaxHeight; ++h) {
            if (update__[h]) {
                auto *x = update__[h]->nex[h];
                update__[h]->nex[h]=this;
                this->nex[h]=x;
                if(x)x->pre[h]=this;
                if(this)this->pre[h]=update__[h];
            }
            if(rand()%Rate) break;
        }
    }

    void print()
    {
        for(auto *p = this->nex[0]; p && p!=this; p=p->nex[0]) {
            cout << "("<<p->key << ":" << p->val<<"), ";
        }
        endl(cout);
    }

};

template<typename ValType>
void skiplist_insert(SkipNode<ValType> &hand,intmax_t key,ValType val)
{
    decltype(hand.update) assist{};
    if(key == hand.upper_bound(key,assist)) {
        assist[0]->nex[0]->val = val;
    } else {
        (new SkipNode<ValType>(key,val))->into(assist);
    }
}

template<typename ValType>
bool skiplist_erase(SkipNode<ValType> &hand,intmax_t key) {
    decltype(hand.update) assist{};
    if (key == hand.upper_bound(key,assist)) {
        delete assist[0]->nex[0]->escape();
        return true;
    }
    return false;
}

void test_insert0()
{
    SkipNode<int> hand;
    hand.init_pos(&hand);
    srand(time(0));
    skiplist_insert<int>(hand,32,78);
    skiplist_insert<int>(hand,36,78);
    skiplist_insert<int>(hand,32,71);
    skiplist_insert<int>(hand,33,78);
    skiplist_insert<int>(hand,311,766);
    hand.print();
}

void test_erase0() {
    SkipNode<int> hand;
    hand.init_pos(&hand);
    srand(time(0));
    skiplist_insert<int>(hand,32,78);
    skiplist_insert<int>(hand,36,78);
    skiplist_insert<int>(hand,32,71);
    skiplist_insert<int>(hand,33,78);
    skiplist_insert<int>(hand,311,766);
    hand.print();
    skiplist_erase(hand,100);
    hand.print();
    skiplist_erase(hand,311);
    hand.print();
}

int main()
{
    test_insert0();
    test_erase0();
    return 0;
}


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