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Create hash_map_open_addressing.c (#838)

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* Create hash_map_open_addressing.c

哈希冲突-C语言

* Update hash_map_open_addressing.c

* Update hash_map_open_addressing.c

* Update hash_map_open_addressing.c
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lclc6
2023-10-13 14:15:23 +08:00
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parent 61eca92055
commit fe01f77ff8
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codes/c/chapter_hashing/hash_map_open_addressing.c Normal file
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/**
* File: hash_map_open_addressing.c
* Created Time: 2023-10-6
* Author: lclc6 (w1929522410@163.com)
*/
#include "../utils/common.h"
/* 开放寻址哈希表 */
struct Pair {
int key;
char *val;
};
typedef struct Pair Pair;
struct HashMapOpenAddressing {
int size; // 键值对数量
int capacity; // 哈希表容量
double loadThres; // 触发扩容的负载因子阈值
int extendRatio; // 扩容倍数
Pair **buckets; // 桶数组
Pair *TOMBSTONE; // 删除标记
};
typedef struct HashMapOpenAddressing HashMapOpenAddressing;
// 函数声明
void extend(HashMapOpenAddressing *hashMap);
/* 构造方法 */
HashMapOpenAddressing *newHashMapOpenAddressing() {
HashMapOpenAddressing *hashMap = (HashMapOpenAddressing *)malloc(sizeof(HashMapOpenAddressing));
hashMap->size = 0;
hashMap->capacity = 4;
hashMap->loadThres = 2.0 / 3.0;
hashMap->extendRatio = 2;
hashMap->buckets = (Pair **)malloc(sizeof(Pair *) * hashMap->capacity);
hashMap->TOMBSTONE = (Pair *)malloc(sizeof(Pair));
hashMap->TOMBSTONE->key = -1;
hashMap->TOMBSTONE->val = "-1";
return hashMap;
}
/* 析构方法 */
void delHashMapOpenAddressing(HashMapOpenAddressing *hashMap) {
for (int i = 0; i < hashMap->capacity; i++) {
Pair *pair = hashMap->buckets[i];
if (pair != NULL && pair != hashMap->TOMBSTONE) {
free(pair->val);
free(pair);
}
}
}
/* 哈希函数 */
int hashFunc(HashMapOpenAddressing *hashMap, int key) {
return key % hashMap->capacity;
}
/* 负载因子 */
double loadFactor(HashMapOpenAddressing *hashMap) {
return (double)hashMap->size / (double)hashMap->capacity;
}
/* 搜索 key 对应的桶索引 */
int findBucket(HashMapOpenAddressing *hashMap, int key) {
int index = hashFunc(hashMap, key);
int firstTombstone = -1;
// 线性探测，当遇到空桶时跳出
while (hashMap->buckets[index] != NULL) {
// 若遇到 key ，返回对应桶索引
if (hashMap->buckets[index]->key == key) {
// 若之前遇到了删除标记，则将键值对移动至该索引
if (firstTombstone != -1) {
hashMap->buckets[firstTombstone] = hashMap->buckets[index];
hashMap->buckets[index] = hashMap->TOMBSTONE;
return firstTombstone; // 返回移动后的桶索引
}
return index; // 返回桶索引
}
// 记录遇到的首个删除标记
if (firstTombstone == -1 && hashMap->buckets[index] == hashMap->TOMBSTONE) {
firstTombstone = index;
}
// 计算桶索引，越过尾部返回头部
index = (index + 1) % hashMap->capacity;
}
// 若 key 不存在，则返回添加点的索引
return firstTombstone == -1 ? index : firstTombstone;
}
/* 查询操作 */
char *get(HashMapOpenAddressing *hashMap, int key) {
// 搜索 key 对应的桶索引
int index = findBucket(hashMap, key);
// 若找到键值对，则返回对应 val
if (hashMap->buckets[index] != NULL && hashMap->buckets[index] != hashMap->TOMBSTONE) {
return hashMap->buckets[index]->val;
}
// 若键值对不存在，则返回空字符串
return "";
}
/* 添加操作 */
void put(HashMapOpenAddressing *hashMap, int key, char *val) {
// 当负载因子超过阈值时，执行扩容
if (loadFactor(hashMap) > hashMap->loadThres) {
extend(hashMap);
}
// 搜索 key 对应的桶索引
int index = findBucket(hashMap, key);
// 若找到键值对，则覆盖 val 并返回
if (hashMap->buckets[index] != NULL && hashMap->buckets[index] != hashMap->TOMBSTONE) {
free(hashMap->buckets[index]->val);
hashMap->buckets[index]->val = (char *)malloc(sizeof(strlen(val + 1)));
strcpy(hashMap->buckets[index]->val, val);
hashMap->buckets[index]->val[strlen(val)] = '\0';
return;
}
// 若键值对不存在，则添加该键值对
Pair *pair = (Pair *)malloc(sizeof(Pair));
pair->key = key;
pair->val = (char *)malloc(sizeof(strlen(val + 1)));
strcpy(pair->val, val);
pair->val[strlen(val)] = '\0';
hashMap->buckets[index] = pair;
hashMap->size++;
}
/* 删除操作 */
void removeItem(HashMapOpenAddressing *hashMap, int key) {
// 搜索 key 对应的桶索引
int index = findBucket(hashMap, key);
// 若找到键值对，则用删除标记覆盖它
if (hashMap->buckets[index] != NULL && hashMap->buckets[index] != hashMap->TOMBSTONE) {
Pair *pair = hashMap->buckets[index];
free(pair->val);
free(pair);
hashMap->buckets[index] = hashMap->TOMBSTONE;
hashMap->size--;
}
}
/* 扩容哈希表 */
void extend(HashMapOpenAddressing *hashMap) {
// 暂存原哈希表
Pair **bucketsTmp = hashMap->buckets;
int oldCapacity = hashMap->capacity;
// 初始化扩容后的新哈希表
hashMap->capacity *= hashMap->extendRatio;
hashMap->buckets = (Pair **)malloc(sizeof(Pair *) * hashMap->capacity);
hashMap->size = 0;
// 将键值对从原哈希表搬运至新哈希表
for (int i = 0; i < oldCapacity; i++) {
Pair *pair = bucketsTmp[i];
if (pair != NULL && pair != hashMap->TOMBSTONE) {
put(hashMap, pair->key, pair->val);
free(pair->val);
free(pair);
}
}
free(bucketsTmp);
}
/* 打印哈希表 */
void print(HashMapOpenAddressing *hashMap) {
for (int i = 0; i < hashMap->capacity; i++) {
Pair *pair = hashMap->buckets[i];
if (pair == NULL) {
printf("NULL\n");
} else if (pair == hashMap->TOMBSTONE) {
printf("TOMBSTONE\n");
} else {
printf("%d -> %s\n", pair->key, pair->val);
}
}
}
/* Driver Code */
int main() {
// 初始化哈希表
HashMapOpenAddressing *hashmap = newHashMapOpenAddressing();
// 添加操作
// 在哈希表中添加键值对 (key, val)
put(hashmap, 12836, "小哈");
put(hashmap, 15937, "小啰");
put(hashmap, 16750, "小算");
put(hashmap, 13276, "小法");
put(hashmap, 10583, "小鸭");
printf("\n添加完成后，哈希表为\nKey -> Value\n");
print(hashmap);
// 查询操作
// 向哈希表输入键 key ，得到值 val
char *name = get(hashmap, 13276);
printf("\n输入学号 13276 ，查询到姓名 %s\n", name);
// 删除操作
// 在哈希表中删除键值对 (key, val)
removeItem(hashmap, 16750);
printf("\n删除 16750 后，哈希表为\nKey -> Value\n");
print(hashmap);
// 销毁哈希表
delHashMapOpenAddressing(hashmap);
return 0;
}