data_structure_and_algorithm -- 跳錶：python & java & c-cpp 實現
阿新 • • 發佈：2019-01-10
當開始深入的研究資料結構和演算法你會愛上它。
下面是python實現程式碼，後面要記得加註釋啊啊啊
from typing import Optional import random class ListNode: def __init__(self, data: Optional[int] = None): self._data = data self._forwards = [] # Forward pointers class SkipList: _MAX_LEVEL = 16 def __init__(self): self._level_count = 1 self._head = ListNode() self._head._forwards = [None] * type(self)._MAX_LEVEL def find(self, value: int) -> Optional[ListNode]: p = self._head for i in range(self._level_count - 1, -1, -1): # Move down a level while p._forwards[i] and p._forwards[i]._data < value: p = p._forwards[i] # Move along level return p._forwards[0] if p._forwards[0] and p._forwards[0]._data == value else None def insert(self, value: int): level = self._random_level() if self._level_count < level: self._level_count = level new_node = ListNode(value) new_node._forwards = [None] * level update = [self._head] * level # update is like a list of prevs p = self._head for i in range(level - 1, -1, -1): while p._forwards[i] and p._forwards[i]._data < value: p = p._forwards[i] update[i] = p # Found a prev for i in range(level): new_node._forwards[i] = update[i]._forwards[i] # new_node.next = prev.next update[i]._forwards[i] = new_node # prev.next = new_node def delete(self, value): update = [None] * self._level_count p = self._head for i in range(self._level_count - 1, -1, -1): while p._forwards[i] and p._forwards[i]._data < value: p = p._forwards[i] update[i] = p if p._forwards[0] and p._forwards[0]._data == value: for i in range(self._level_count - 1, -1, -1): if update[i]._forwards[i] and update[i]._forwards[i]._data == value: update[i]._forwards[i] = update[i]._forwards[i]._forwards[i] # Similar to prev.next = prev.next.next def _random_level(self, p: float = 0.5) -> int: level = 1 while random.random() < p and level < type(self)._MAX_LEVEL: level += 1 return level def __repr__(self) -> str: values = [] p = self._head while p._forwards[0]: values.append(str(p._forwards[0]._data)) p = p._forwards[0] return "->".join(values) if __name__ == "__main__": l = SkipList() for i in range(10): l.insert(i) print(l) p = l.find(7) print(p._data) l.delete(3) print(l)
java實現：
package skiplist; import java.util.Random; /** * 跳錶的一種實現方法。 * 跳錶中儲存的是正整數，並且儲存的是不重複的。 * * Author：ZHENG */ public class SkipList { private static final int MAX_LEVEL = 16; private int levelCount = 1; private Node head = new Node(); // 帶頭連結串列 private Random r = new Random(); public Node find(int value) { Node p = head; for (int i = levelCount - 1; i >= 0; --i) { while (p.forwards[i] != null && p.forwards[i].data < value) { p = p.forwards[i]; } } if (p.forwards[0] != null && p.forwards[0].data == value) { return p.forwards[0]; } else { return null; } } public void insert(int value) { int level = randomLevel(); Node newNode = new Node(); newNode.data = value; newNode.maxLevel = level; Node update[] = new Node[level]; for (int i = 0; i < level; ++i) { update[i] = head; } Node p = head; for (int i = level - 1; i >= 0; --i) { while (p.forwards[i] != null && p.forwards[i].data < value) { p = p.forwards[i]; } update[i] = p; } for (int i = 0; i < level; ++i) { newNode.forwards[i] = update[i].forwards[i]; update[i].forwards[i] = newNode; } if (levelCount < level) levelCount = level; } public void delete(int value) { Node[] update = new Node[levelCount]; Node p = head; for (int i = levelCount - 1; i >= 0; --i) { while (p.forwards[i] != null && p.forwards[i].data < value) { p = p.forwards[i]; } update[i] = p; } if (p.forwards[0] != null && p.forwards[0].data == value) { for (int i = levelCount - 1; i >= 0; --i) { if (update[i].forwards[i] != null && update[i].forwards[i].data == value) { update[i].forwards[i] = update[i].forwards[i].forwards[i]; } } } } private int randomLevel() { int level = 1; for (int i = 1; i < MAX_LEVEL; ++i) { if (r.nextInt() % 2 == 1) { level++; } } return level; } public void printAll() { Node p = head; while (p.forwards[0] != null) { System.out.print(p.forwards[0] + " "); p = p.forwards[0]; } System.out.println(); } public class Node { private int data = -1; private Node forwards[] = new Node[MAX_LEVEL]; private int maxLevel = 0; @Override public String toString() { StringBuilder builder = new StringBuilder(); builder.append("{ data: "); builder.append(data); builder.append("; levels: "); builder.append(maxLevel); builder.append(" }"); return builder.toString(); } } }
c實現：
#include <stdio.h> #include <stdlib.h> #include <stdbool.h> #include <string.h> #include <time.h> // https://www.youtube.com/watch?v=2g9OSRKJuzM&t=17s #define MAX_LEVEL 15 struct node { int val; int max_level; struct node *forward[MAX_LEVEL]; }; struct skip_list { struct node head; int max_level; int max_level_nodes; }; void node_init(struct node* node) { memset(node, 0, sizeof(struct node)); } void skip_list_init(struct skip_list* sl) { node_init(&sl->head); sl->max_level = 0; sl->max_level_nodes = 0; } void random_init() { static bool done = false; if (done) return; srandom(time(NULL)); done = true; } int random_level(void) { int i, level = 1; random_init(); for (i = 1; i < MAX_LEVEL; i++) if (random() % 2 == 1) level++; return level; } void random_level_test() { printf("random level %d\n", random_level()); printf("random level %d\n", random_level()); printf("random level %d\n", random_level()); printf("random level %d\n", random_level()); printf("random level %d\n", random_level()); } void insert(struct skip_list *sl, int val) { int level = random_level(); struct node *update[MAX_LEVEL]; struct node *new, *p; int i; new = (struct node*)malloc(sizeof(struct node)); if (!new) return; new->max_level = level; new->val = val; for (int i = 0; i < MAX_LEVEL; i++) update[i] = &sl->head; p = &sl->head; for (i = level - 1; i >= 0; i--) { while(p->forward[i] && p->forward[i]->val < val) p = p->forward[i]; update[i] = p; } for (i = 0; i < level; i++) { new->forward[i] = update[i]->forward[i]; update[i]->forward[i] = new; } if (sl->max_level < level) { sl->max_level = level; sl->max_level_nodes = 1; } else if (sl->max_level == level) sl->max_level_nodes++; } struct node *find(struct skip_list* sl, int val) { struct node *node = &sl->head; int i; for (i = sl->max_level - 1; i >= 0; i--) { while (node->forward[i] && node->forward[i]->val < val) node = node->forward[i]; } if (node->forward[0] && node->forward[0]->val == val) { return node->forward[0]; } else return NULL; } void delete(struct skip_list* sl, int val) { struct node *update[MAX_LEVEL]; struct node *p; int i; p = &sl->head; for (i = sl->max_level; i >= 0; i--) { while (p->forward[i] && p->forward[i]->val < val) p = p->forward[i]; update[i] = p; } if (p->forward[0] == NULL || p->forward[0]->val != val) return; if (p->forward[0]->max_level == sl->max_level) sl->max_level_nodes--; for (i = sl->max_level-1; i >= 0; i--) { if (update[i]->forward[i] && update[i]->forward[i]->val == val) update[i]->forward[i] = update[i]->forward[i]->forward[i]; } // fixup max_level and max_level_nodes if (sl->max_level_nodes == 0) { //sl->max_level--; p = &sl->head; // skip (max_level - 1), direct test (max_level - 2) // since no nodes on (max_level - 1) for (i = sl->max_level - 2; i >= 0; i--) { while (p->forward[i]) { sl->max_level_nodes++; p = p->forward[i]; } if (sl->max_level_nodes) { sl->max_level = i + 1; break; } else sl->max_level = i; } } } void print_sl(struct skip_list* sl) { struct node *node; int level; printf("%d level skip list with %d nodes on top\n", sl->max_level, sl->max_level_nodes); for (level = sl->max_level - 1; level >= 0; level--) { node = &sl->head; printf("Level[%02d]:", level); while (node->forward[level]) { printf("%4d", node->forward[level]->val); node = node->forward[level]; } printf("\n"); } } int main() { struct skip_list sl; struct node *node = NULL; int i; skip_list_init(&sl); print_sl(&sl); for (i = 0; i < 10; i++) insert(&sl, i); print_sl(&sl); node = find(&sl, 8); if (node) printf("find 8 in sl %d\n", node->val); else printf("8 not in sl\n"); for (i = 0; i < 10; i++) { delete(&sl, i); print_sl(&sl); } return 0; }
c++實現：
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#include <cstring>
#include <random>
#include <ctime>
using namespace std;
/**
* 跳錶的一種實現方法。
* 跳錶中儲存的是正整數，並且儲存的是不重複的。
*
* 跳錶的C++版本.
* 翻譯JAVA版本 原作者 Author：ZHENG
*
* Author：puhuaqiang
*
* 跳錶結構:
*
* 第K級 1 9
* 第K-1級 1 5 9
* 第K-2級 1 3 5 7 9
* ... ....
* 第0級(原始連結串列) 1 2 3 4 5 6 7 8 9
*/
const int MAX_LEVEL = 16;
/**
* @brief 節點
*/
class CNode
{
public:
CNode();
~CNode();
std::string toString();
/**
* @brief 獲取索引連結串列
*/
CNode** GetIdxList();
/**
* @brief 設定資料
*/
void SetData(int v);
/**
* @brief 獲取資料
*/
int GetData();
/**
* @brief 設定最大索引級別
*/
void SetLevel(int l);
private:
/**當前節點的值*/
int m_data;
/**
* 當前節點的每個等級的下一個節點.
* 第2級 N1 N2
* 第1級 N1 N2
* 如果N1是本節點,則 m_lpForwards[x] 儲存的是N2
*
* [0] 就是原始連結串列.
*/
CNode* m_lpForwards[MAX_LEVEL];
/**當前節點的所在的最大索引級別*/
int m_iMaxLevel;
};
/**
* @brief 跳錶
*/
class CSkipList
{
public:
CSkipList();
~CSkipList();
/**
* @brief 查詢指定的值的節點
* @param v 正整數
*/
CNode* Find(int v);
/**
* @brief 插入指定的值
* @param v 正整數
*/
void Insert(int v);
/**
* @brief 刪除指定的值的節點
* @param v 正整數
*/
int Delete(int v);
void PrintAll();
/**
* @brief 列印跳錶結構
* @param l 等於-1時列印所有級別的結構 >=0時列印指定級別的結構
*/
void PrintAll(int l);
/**
* @brief 插入節點時,得到插入K級的隨機函式
* @return K
*/
int RandomLevel();
private:
int levelCount;
/**
* 連結串列
* 帶頭/哨所(節點)
*/
CNode* m_lpHead;
};
int main()
{
CSkipList skipList;
/// 插入原始值
for(int i=1; i< 50; i++){
if((i%3) == 0){
skipList.Insert(i);
}
}
for(int i=1; i< 50; i++){
if((i%3) == 1){
skipList.Insert(i);
}
}
skipList.PrintAll();
std::cout<<std::endl;
/// 列印所有等級結構
skipList.PrintAll(-1);
/// 查詢
std::cout<<std::endl;
CNode* lpNode = skipList.Find(27);
if(NULL != lpNode){
std::cout<<"查詢值為27的節點,找到該節點,節點值:"<<lpNode->GetData()<<std::endl;
}else{
std::cout<<"查詢值為27的節點,未找到該節點"<<std::endl;
}
/// 刪除
std::cout<<std::endl;
int ret = skipList.Delete(46);
if(0 == ret){
std::cout<<"查詢值為46的節點,找到該節點,並刪除成功"<<std::endl;
}else{
std::cout<<"查詢值為46的節點,找到該節點,刪除失敗"<<std::endl;
}
std::cout<<std::endl;
//列印所有等級結構
skipList.PrintAll(-1);
std::cin.ignore();
return 0;
}
CNode::CNode()
{
m_data = -1;
m_iMaxLevel = 0;
for(int i=0; i<MAX_LEVEL; i++){
m_lpForwards[i] = NULL;
}
}
CNode::~CNode()
{
}
CNode** CNode::GetIdxList()
{
return m_lpForwards;
}
void CNode::SetData(int v)
{
m_data = v;
}
int CNode::GetData()
{
return m_data;
}
void CNode::SetLevel(int l)
{
m_iMaxLevel = l;
}
std::string CNode::toString()
{
char tmp[32];
std::string ret;
ret.append("{ data: ");
sprintf(tmp, "%d", m_data);
ret.append(tmp);
ret.append("; levels: ");
sprintf(tmp, "%d", m_iMaxLevel);
ret.append(tmp);
ret.append(" }");
return ret;
}
CSkipList::CSkipList()
{
levelCount = 1;
m_lpHead = new CNode();
}
CSkipList::~CSkipList()
{
}
CNode* CSkipList::Find(int v)
{
CNode* lpNode = m_lpHead;
/**
* 從 最大級索引連結串列開始查詢.
* K -> k-1 -> k-2 ...->0
*/
for(int i=levelCount-1; i>=0; --i){
/**
* 查詢小於v的節點(lpNode).
*/
while((NULL != lpNode->GetIdxList()[i]) && (lpNode->GetIdxList()[i]->GetData() < v)){
lpNode = lpNode->GetIdxList()[i];
}
}
/**
* lpNode 是小於v的節點, lpNode的下一個節點就等於或大於v的節點
*/
if((NULL != lpNode->GetIdxList()[0]) && (lpNode->GetIdxList()[0]->GetData() == v)){
return lpNode->GetIdxList()[0];
}
return NULL;
}
void CSkipList::Insert(int v)
{
/// 新節點
CNode* lpNewNode = new CNode();
if(NULL == lpNewNode){
return;
}
/**
* 新節點最大分佈在的索引連結串列的上限
* 如果返回 3,則 新的節點會在索引1、2、3上的連結串列都存在
*/
int level = RandomLevel();
lpNewNode->SetData(v);
lpNewNode->SetLevel(level);
/**
* 臨時索引連結串列
* 主要是得到新的節點在每個索引連結串列上的位置
*/
CNode *lpUpdateNode[level];
for(int i=0; i<level; i++){
/// 每個索引連結串列的頭節點
lpUpdateNode[i] =m_lpHead;
}
CNode* lpFind = m_lpHead;
for(int i= level-1; i >= 0; --i){
/**
* 查詢位置
* eg. 第1級 1 7 10
* 如果插入的是 6
* lpFind->GetIdxList()[i]->GetData() : 表示節點lpFind在第1級索引的下一個節點的資料
* 當 "lpFind->GetIdxList()[i]->GetData() < v"不成立的時候,
* 新節點就要插入到 lpFind節點的後面, lpFind->GetIdxList()[i] 節點的前面
* 即在這裡 lpFind就是1 lpFind->GetIdxList()[i] 就是7
*/
while((NULL != lpFind->GetIdxList()[i]) && (lpFind->GetIdxList()[i]->GetData() < v)){
lpFind = lpFind->GetIdxList()[i];
}
/// lpFind 是新節點在 第i級索引連結串列的後一個節點
lpUpdateNode[i] = lpFind;
}
for(int i=0; i<level; ++i){
/**
* 重新設定連結串列指標位置
* eg 第1級索引 1 7 10
* 插入6.
* lpUpdateNode[i] 節點是1; lpUpdateNode[i]->GetIdxList()[i]節點是7
*
* 這2句程式碼就是 把6放在 1和7之間
*/
lpNewNode->GetIdxList()[i] = lpUpdateNode[i]->GetIdxList()[i];
lpUpdateNode[i]->GetIdxList()[i] = lpNewNode;
}
if(levelCount < level){
levelCount = level;
}
}
int CSkipList::Delete(int v)
{
int ret = -1;
CNode *lpUpdateNode[levelCount];
CNode *lpFind = m_lpHead;
for(int i=levelCount-1; i>= 0; --i){
/**
* 查詢小於v的節點(lpFind).
*/
while((NULL != lpFind->GetIdxList()[i]) && (lpFind->GetIdxList()[i]->GetData() < v)){
lpFind = lpFind->GetIdxList()[i];
}
lpUpdateNode[i] = lpFind;
}
/**
* lpFind 是小於v的節點, lpFind的下一個節點就等於或大於v的節點
*/
if((NULL != lpFind->GetIdxList()[0]) && (lpFind->GetIdxList()[0]->GetData() == v)){
for(int i=levelCount-1; i>=0; --i){
if((NULL != lpUpdateNode[i]->GetIdxList()[i]) && (v == lpUpdateNode[i]->GetIdxList()[i]->GetData())){
lpUpdateNode[i]->GetIdxList()[i] = lpUpdateNode[i]->GetIdxList()[i]->GetIdxList()[i];
ret = 0;
}
}
}
return ret;
}
void CSkipList::PrintAll()
{
CNode* lpNode = m_lpHead;
while(NULL != lpNode->GetIdxList()[0]){
std::cout<<lpNode->GetIdxList()[0]->toString().data()<<std::endl;
lpNode = lpNode->GetIdxList()[0];
}
}
void CSkipList::PrintAll(int l)
{
for(int i=MAX_LEVEL-1; i>=0;--i){
CNode* lpNode = m_lpHead;
std::cout<<"第"<<i<<"級:"<<std::endl;
if((l < 0) || ((l >= 0) && (l == i))){
while(NULL != lpNode->GetIdxList()[i]){
std::cout<<lpNode->GetIdxList()[i]->GetData()<<" ";
lpNode = lpNode->GetIdxList()[i];
}
std::cout<<std::endl;
if(l >= 0){
break;
}
}
}
}
int GetRandom()
{
static int _count = 1;
std::default_random_engine generator(time(0) + _count);
std::uniform_int_distribution<int> distribution(1,99999/*0x7FFFFFFF*/);
int dice_roll = distribution(generator);
_count += 100;
return dice_roll;
}
int CSkipList::RandomLevel()
{
int level = 1;
for(int i=1; i<MAX_LEVEL; ++i){
if(1 == (GetRandom()%3)){
level++;
}
}
return level;
}參考：