Redis数据结构—跳跃表 skiplist
跳跃表(skiplist)是Redis中的一种数据结构,它允许快速的插入、删除、查找操作,在实现上是一种可以替代平衡树的数据结构,在查询速度上有可比的优势。
以下是一个简单的C语言实现的跳跃表节点和跳跃表结构的示例代码:
#include <stdlib.h>
// 跳跃表节点结构体
typedef struct skiplistNode {
int key;
struct skiplistNode *backward;
struct skiplistNode *next[];
} skiplistNode;
// 跳跃表结构体
typedef struct skiplist {
skiplistNode *header;
int level;
} skiplist;
// 创建一个新的跳跃表节点
skiplistNode *createNode(int key, int level) {
skiplistNode *node = malloc(sizeof(skiplistNode) + level * sizeof(skiplistNode*));
node->key = key;
node->backward = NULL;
for(int i = 0; i < level; i++) {
node->next[i] = NULL;
}
return node;
}
// 初始化一个跳跃表
skiplist *initSkipList() {
skiplist *list = malloc(sizeof(skiplist));
list->header = createNode(0, 32); // 假设最大层数为32
list->header->backward = NULL;
list->level = 0;
return list;
}
// 插入一个新的节点到跳跃表
void insert(skiplist *list, int key) {
skiplistNode *update[32];
skiplistNode *node = list->header;
int level = list->level;
for(int i = level; i >= 0; i--) {
while(node->next[i] && node->next[i]->key < key) {
node = node->next[i];
}
update[i] = node;
}
if(node->next[0] && node->next[0]->key == key) {
// 如果键值已存在,不做操作
} else {
int newLevel = randomLevel(); // 假设randomLevel函数用于生成新节点的层数
if(newLevel > level) {
for(int i = level + 1; i <= newLevel; i++) {
update[i] = list->header;
}
level = newLevel;
}
skiplistNode *newNode = createNode(key, newLevel);
for(int i = 0; i < newLevel; i++) {
newNode->next[i] = update[i]->next[i];
update[i]->next[i] = newNode;
newNode->backward = update[i];
if(newNode->next[i]) {
newNode->next[i]->backward = newNode;
}
}
if(level > list->level) {
list->level = level;
}
}
}
// 查找一个节点
skiplistNode *search(skiplist *list, int key) {
skiplistNode *node = list->header;
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