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skiplist.cpp
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203 lines (181 loc) · 3.76 KB
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#include "skiplist.h"
#include <time.h>
#include <chrono>
#include <random>
skiplist::skiplist():max_level_(1)
{
head_ = new node_t(INT_MIN, 1);
srand(time(0));
}
skiplist::~skiplist()
{
auto p = head_;
while (p)
{
auto d = p;
p = p->next[0];
delete d;
}
}
void skiplist::insert(int val)
{
int level = random_generate_level();
auto p = new node_t(val, level);
node_t** pre = new node_t*[level];
for (int i = 0; i < level; ++i)
{
pre[i] = head_;
}
//
node_t* cur = head_;
for (auto i = level - 1; i >= 0; --i)//最高层开始
{
//每层遍历 找到小于val的最后一个节点
while (cur->next[i] != nullptr && cur->next[i]->val < val)
cur = cur->next[i];
//
pre[i] = cur;
}
//
for (size_t i = 0; i < level; i++)
{
p->next[i] = pre[i]->next[i];
pre[i]->next[i] = p;
}
max_level_ = level > max_level_ ? level : max_level_;
delete[] pre;
}
void skiplist::earse(int val)
{
node_t** pre = new node_t*[SKIP_LIST_MAX_LEVEL];
for (auto i = 0; i < SKIP_LIST_MAX_LEVEL; ++i)
{
pre[i] = nullptr;
}
auto cur = head_;
for (auto i = max_level_ - 1; i >= 0; i--)//最高层开始
{
//每层遍历 找到小于val的最后一个节点
while (cur->next[i] != nullptr && cur->next[i]->val < val)
cur = cur->next[i];
//
pre[i] = cur;
}
//
if (cur->next[0] != nullptr && cur->next[0]->val == val)
{
auto t = cur->next[0];
for (auto i = SKIP_LIST_MAX_LEVEL - 1; i >= 0; i--)
{
if (pre[i] == nullptr)
continue;
//
if (pre[i]->next[i] != nullptr && pre[i]->next[i]->val == val)
pre[i]->next[i] = pre[i]->next[i]->next[i];
}
delete t;
}
//
while (max_level_ > 1 && head_->next[max_level_ - 1] == nullptr)
--max_level_;
delete[] pre;
}
int skiplist::rank(int val)
{
node_t* p = head_;
int r = 0;
while (p->next[0] != nullptr && p->next[0]->val < val)
{
p = p->next[0];
r++;
}
return r;
}
int skiplist::rank(int val, node_t*& lower, node_t* &upper)
{
lower = lower_bound(val);
upper = upper_bound(val);
return rank(val);
}
node_t* skiplist::get(int idx)
{
node_t* p = head_;
int r = 0;
while (p->next[0] != nullptr && --idx)
{
p = p->next[0];
}
//
if (idx == 0)
return p;
return nullptr;
}
node_t* skiplist::find(int key)
{
auto p = head_;
for (size_t i = 0; i < max_level_; i++) // lower_bound
{
while (p->next[i] && p->next[i]->val < key)
p = p->next[i];
}
if (p->next[0] != nullptr && p->next[0]->val == key)
{
return p->next[0];
}
return nullptr;
}
void skiplist::print()
{
for (auto i = max_level_ - 1; i >=0; --i)
{
auto p = head_->next[i];
printf("Level %d: %d", i, head_->val);
while (p)
{
printf("-> %d", p->val);
p = p->next[i];
}
printf("\n");
}
printf("\n");
}
size_t skiplist::level()
{
return max_level_;
}
int skiplist::random_generate_level()
{
int level = 1;
const unsigned int seed = std::chrono::system_clock::now().time_since_epoch().count(); //获取系统时间戳，单位微秒(microsecond)。
std::default_random_engine generator(seed); //系统时间戳作为种子
std::uniform_real_distribution<float> distribution(0, 1);
float random_num = distribution(generator); //均匀分布，生成区间[0,1]的浮点数
while (random_num < rate_ && level < SKIP_LIST_MAX_LEVEL) { //模拟每一次都是50%的概率小于probability
random_num = distribution(generator);
++level;
}
return level;
}
node_t* skiplist::lower_bound(int val)
{
node_t* p = head_;
for (auto i = max_level_ - 1; i >= 0; i--)//最高层开始
{
//每层遍历 找到小于val的最后一个节点
while (p->next[i] != nullptr && p->next[i]->val < val)
p = p->next[i];
}
return p;
}
node_t* skiplist::upper_bound(int val)
{
node_t* p = head_;
for (auto i = max_level_ - 1; i >= 0; i--)//最高层开始
{
//每层遍历 找到小于val的最后一个节点
while (p->next[i] != nullptr && p->next[i]->val <= val)
p = p->next[i];
}
//
return p->next[0]; //第一个大于 val
}