From fe01f77ff8b07aa8a7a8083ab7605cda68043990 Mon Sep 17 00:00:00 2001 From: lclc6 <95404740+lclc6@users.noreply.github.com> Date: Fri, 13 Oct 2023 14:15:23 +0800 Subject: [PATCH] Create hash_map_open_addressing.c (#838) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit * 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 --- .../hash_map_open_addressing.c | 211 ++++++++++++++++++ 1 file changed, 211 insertions(+) create mode 100644 codes/c/chapter_hashing/hash_map_open_addressing.c diff --git a/codes/c/chapter_hashing/hash_map_open_addressing.c b/codes/c/chapter_hashing/hash_map_open_addressing.c new file mode 100644 index 00000000..0979d225 --- /dev/null +++ b/codes/c/chapter_hashing/hash_map_open_addressing.c @@ -0,0 +1,211 @@ +/** + * 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; +}