Create hash_map_open_addressing.c (#838)

* 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
2023-10-13 14:15:23 +08:00 · 2023-10-13 14:15:23 +08:00 · fe01f77ff8
commit fe01f77ff8
parent 61eca92055
1 changed files with 211 additions and 0 deletions
--- a/codes/c/chapter_hashing/hash_map_open_addressing.c
+++ 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;
+}