c++实现跳跃表（Skip List）的方法示例

typedef struct nodeStructure *node;
typedef struct nodeStructure
{
 keyType key; // key值
 valueType value; // value值
 // 向前指针数组，根据该节点层数的
 // 不同指向不同大小的数组
 node forward[1]; 
};

// 定义跳表数据类型
typedef struct listStructure{
 int level; 
 struct nodeStructure * header;
} * list; 

//
// skiplist_def.h
// test
//
// Created by 杜国超 on 17/9/24.
// Copyright © 2017年 杜国超. All rights reserved.
//

#ifndef skiplist_def_h
#define skiplist_def_h

#define MAX_LEVEL 8
typedef int KeyType;
typedef int ValueType;

//定义节点信息数据结构
template <typename K,typename V>
struct NodeStructure {
 K key;
 V value;
 NodeStructure* forward[1];
};

//定义跳跃表数据结构
template <typename K,typename V>
struct SkipLisStructure{
 int level;
 NodeStructure<K,V>* header;
};

typedef struct NodeStructure<KeyType,ValueType> NodeType;
typedef struct SkipLisStructure<KeyType,ValueType> ListType;

typedef NodeType* Node;
typedef ListType* List;


#define NEW_LEVEL_NODE(level) (Node)malloc(sizeof(NodeType) + (level) * sizeof(Node))


#endif /* skiplist_def_h */

//
// skiplist.h
// test
//
// Created by 杜国超 on 17/9/24.
// Copyright © 2017年 杜国超. All rights reserved.
//

#ifndef skiplist_h
#define skiplist_h

#include "skiplist_def.h"


class CSkipList{
public:
 CSkipList();
 ~CSkipList();
public:
 ValueType* Search(const KeyType& key);
 bool Insert(KeyType& key,ValueType& value);
 bool Delete(const KeyType& key,ValueType& value);
 void FreeList();

private:
 int RandomLevel();
private:
 List _skipList;
 int _size;
 
};

 
#endif /* skiplist_h */

//
// skiplist.cpp
// test
//
// Created by 杜国超 on 17/9/24.
// Copyright © 2017年 杜国超. All rights reserved.
//

#include "skiplist_def.h"
#include "skiplist.h"
#include <stdlib.h>

CSkipList::CSkipList(){
 _skipList = (List)malloc(sizeof(ListType));
 // 设置跳表的层level，初始的层为0层（数组从0开始）
 _skipList->level = 0;
 _skipList->header = NEW_LEVEL_NODE(MAX_LEVEL);
 // 将header的forward数组清空
 for(int i = 0; i < MAX_LEVEL; ++i)
  _skipList->header->forward[i] = NULL;
 _size = 0;
}

CSkipList::~CSkipList()
{
 FreeList();
}

ValueType* CSkipList::Search(const KeyType& key){
 Node node = _skipList->header;
 Node indexNode = NULL;
 for(int i = _skipList->level - 1; i >= 0; --i){
  while((indexNode = node->forward[i]) && (indexNode->forward[i]->key <= key))
  {
   if (indexNode->key == key)
   {
    return &(indexNode->value);
   }
   node = indexNode;
  }
 }
 return NULL;
}


bool CSkipList::Insert(KeyType& key, ValueType& value)
{
 Node update[MAX_LEVEL];
 int i;
 Node node = _skipList->header;
 Node indexNode = NULL;
 //寻找key所要插入的位置
 for(i = _skipList->level - 1; i >= 0; --i){
  while((indexNode = node->forward[i]) && (indexNode->forward[i]->key < key))
  {
   node = indexNode;
  }
  update[i] = node;
 }
 node = node->forward[0];
 //如果key已经存在
 if(node->key == key){
  node->value = value;
  return false;
 }else{
  //随机生成新结点的层数
  int level = RandomLevel();
  if(level > _skipList->level){
   for (int i = _skipList->level;i < level;++i)
   {
    update[i] = _skipList->header;
   }
   _skipList->level = level;
  }
  
  //申请新的结点
  Node newNode = NEW_LEVEL_NODE(level);
  newNode->key = key;
  newNode->value = value;
 
  //调整forward指针
  for(int i = level - 1; i >= 0; --i){
   node = update[i];
   newNode->forward[i] = node->forward[i];
   node->forward[i] = newNode;
  }
 
  //更新元素数目
  ++_size;
  return true;
 }
}

bool CSkipList::Delete(const KeyType& key,ValueType& value){
 Node update[MAX_LEVEL];
 int i;
 Node node = _skipList->header;
 Node indexNode = NULL;
 //寻找key所要插入的位置
 for(i = _skipList->level - 1; i >= 0; --i){
  while((indexNode = node->forward[i]) && (indexNode->forward[i]->key < key))
  {
   node = indexNode;
  }
  update[i] = node;
 }
 node = node->forward[0];
 //结点不存在
 if(node->key != key){
  return false;
 }else{
  value = node->value;
  //调整指针
  for(i = 0; i < _skipList->level; ++i){
   if(update[i]->forward[i] != node)
    break;
   update[i]->forward[i] = node->forward[i];
  }
  //删除结点
  free(node);
  for(int i = _skipList->level - 1; i >= 0; i--){
   if(_skipList->header->forward[i]==NULL){
    _skipList->level--;
   }
  }
  //更新链表元素数目
  --_size;
  return true;
 } 
}

int CSkipList::RandomLevel()
{
 int k = 1;
 while (rand()%2)
 {
  k++;
 }
 k=(k<MAX_LEVEL)?k:MAX_LEVEL;
 return k;
}


void CSkipList::FreeList(){
 Node p = _skipList->header;
 Node q;
 while(p != NULL){
  q = p->forward[0];
  free(p);
  p = q;
 }
 free(p);
 free(_skipList);
 _size = 0;
}