feat: Add C codes for chapter_hashing (krahets#706)

* feat: Add C codes for chapter_hashing

* fix:Make corrections to the formatting

* fix:Fixing Test Cases

* fix:Fixing Test Cases

* fix:revised format

* Update hash_map_chaining.c

---------

Co-authored-by: Yudong Jin <[email protected]>

codes/c/chapter_hashing/hash_map_chaining.c

@@ -0,0 +1,242 @@
+/**
+ * File: hash_map_chaining.c
+ * Created Time: 2023-08-29
+ * Author: SenMing ([email protected])
+ */
+
+#include "../utils/common.h"
+
+/* 键值对 int->string */
+struct node {
+    int key;
+    char *val;
+    struct node *next; // 下一个元素
+};
+
+typedef struct node Node;
+
+struct pair {
+    Node *node; // 键值对节点
+};
+
+typedef struct pair Pair;
+
+/* 基于数组简易实现的链式地址哈希表 */
+struct hashMapChaining {
+    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
+};
+
+typedef struct hashMapChaining HashMapChaining;
+
+// 函数声明
+void extend(HashMapChaining *hashmap);
+
+/* 初始化桶数组 */
+HashMapChaining *newHashMapChaining() {
+    // 为哈希表分配空间
+    int tableSize = 4;
+    HashMapChaining *hashmap = (HashMapChaining *)malloc(sizeof(HashMapChaining));
+
+    // 初始化数组
+    hashmap->buckets = (Pair *)malloc(sizeof(Pair) * tableSize);
+    memset(hashmap->buckets, 0, sizeof(Pair) * tableSize);
+
+    hashmap->capacity = tableSize;
+    hashmap->size = 0;
+    hashmap->extendRatio = 2;
+    hashmap->loadThres = 2.0 / 3;
+
+    return hashmap;
+}
+
+/* 销毁哈希表 */
+void delHashMapChaining(HashMapChaining *hashmap) {
+    for (int i = 0; i < hashmap->capacity; i++) {
+        Pair *pair = &hashmap->buckets[i];
+        Node *node = pair->node;
+        while (node != NULL) {
+            Node *temp = node;
+            node = node->next;
+            free(temp->val);
+            free(temp);
+        }
+    }
+    free(hashmap->buckets);
+    free(hashmap);
+}
+
+/* 哈希函数 */
+int hashFunc(HashMapChaining *hashmap, const int key) {
+    return key % hashmap->capacity;
+}
+
+/* 负载因子 */
+double loadFactor(HashMapChaining *hashmap) {
+    return (double)hashmap->size / (double)hashmap->capacity;
+}
+
+/* 查询操作 */
+const char *get(HashMapChaining *hashmap, const int key) {
+    int index = hashFunc(hashmap, key);
+    Pair *pair = &hashmap->buckets[index];
+    Node *node = pair->node;
+    while (node != NULL) {
+        if (node->key == key) {
+            return node->val;
+        }
+    }
+    return NULL;
+}
+
+/* 添加操作 */
+void put(HashMapChaining *hashmap, const int key, char *val) {
+    if (loadFactor(hashmap) > hashmap->loadThres) {
+        extend(hashmap);
+    }
+    int index = hashFunc(hashmap, key);
+
+    // 先为新节点分配空间再赋值
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    memset(newNode, 0, sizeof(Node));
+    newNode->key = key;
+    newNode->val = (char *)malloc(strlen(val) + 1);
+    strcpy(newNode->val, val);
+    newNode->val[strlen(val)] = '\0';
+
+    Pair *pair = &hashmap->buckets[index];
+    Node *node = pair->node;
+    if (node == NULL) {
+        hashmap->buckets[index].node = newNode;
+        hashmap->size++;
+        return;
+    }
+    while (node != NULL) {
+        if (node->key == key) {
+            // 释放先前分配的内存
+            free(node->val);
+            // 更新节点的值
+            node->val = (char *)malloc(strlen(val) + 1);
+            strcpy(node->val, val);
+            node->val[strlen(val)] = '\0';
+            return;
+        }
+        if (node->next == NULL) {
+            break;
+        }
+        node = node->next;
+    }
+    node->next = newNode;
+    hashmap->size++;
+}
+
+/* 删除操作 */
+void removeItem(HashMapChaining *hashmap, int key) {
+    int index = hashFunc(hashmap, key);
+    Pair *pair = &hashmap->buckets[index];
+    Node *node = pair->node;
+    // 保存后继的节点
+    Node *prev = NULL;
+    while (node != NULL) {
+        if (node->key == key) {
+            // 如果要删除的节点是桶的第一个节点
+            if (prev == NULL) {
+                pair->node = node->next;
+            } else {
+                prev->next = node->next;
+            }
+            // 释放内存
+            free(node->val);
+            free(node);
+            hashmap->size--;
+            return;
+        }
+        prev = node;
+        node = node->next;
+    }
+    return;
+}
+
+/* 扩容哈希表 */
+void extend(HashMapChaining *hashmap) {
+    // 暂存原哈希表
+    Pair *oldBuckets = hashmap->buckets;
+    int oldCapacity = hashmap->capacity;
+
+    // 创建新的哈希表，重新分配一段空间
+    hashmap->capacity *= hashmap->extendRatio;
+    hashmap->buckets = (Pair *)malloc(sizeof(Pair) * hashmap->capacity);
+    memset(hashmap->buckets, 0, sizeof(Pair) * hashmap->capacity);
+    hashmap->size = 0;
+
+    // 将原哈希表中的键值对重新哈希到新的哈希表中
+    for (int i = 0; i < oldCapacity; i++) {
+        Node *node = oldBuckets[i].node;
+        while (node != NULL) {
+            put(hashmap, node->key, node->val);
+            node = node->next;
+        }
+    }
+
+    // 释放原哈希表的内存
+    for (int i = 0; i < oldCapacity; i++) {
+        Node *node = oldBuckets[i].node;
+        while (node != NULL) {
+            Node *temp = node;
+            node = node->next;
+            free(temp->val);
+            free(temp);
+        }
+    }
+    free(oldBuckets);
+}
+
+/* 打印哈希表 */
+void print(HashMapChaining *hashmap) {
+    for (int i = 0; i < hashmap->capacity; i++) {
+        printf("[");
+        Pair *pair = &hashmap->buckets[i];
+        Node *node = pair->node;
+        while (node != NULL) {
+            if (node->val != NULL) {
+                printf("%d->%s, ", node->key, node->val);
+            }
+            node = node->next;
+        }
+        printf("]\n");
+    }
+    return;
+}
+
+/* Driver Code */
+int main() {
+    /* 初始化哈希表 */
+    HashMapChaining *map = newHashMapChaining();
+
+    /* 添加操作 */
+    // 在哈希表中添加键值对 (key, value)
+    put(map, 12836, "小哈");
+    put(map, 15937, "小啰");
+    put(map, 16750, "小算");
+    put(map, 13276, "小法");
+    put(map, 10583, "小鸭");
+    printf("\n添加完成后，哈希表为\nKey -> Value\n");
+    print(map);
+
+    /* 查询操作 */
+    // 向哈希表输入键 key ，得到值 value
+    const char *name = get(map, 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, value)
+    removeItem(map, 12836);
+    printf("\n删除 12836 后，哈希表为\nKey -> Value\n");
+    print(map);
+
+    delHashMapChaining(map);
+    return 0;
+}