哈希表

哈希表

例子1：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define TABLE_SIZE 100

// 哈希表中存储的键值对结构体
typedef struct KeyValuePair {
    char* key;
    int value;
    struct KeyValuePair* next; // 指向下一个键值对的指针
} KeyValuePair;

// 哈希表结构体
typedef struct {
    KeyValuePair* table[TABLE_SIZE];
} HashTable;

// 计算哈希值
int hash(char* key) {
    int hash = 0;
    for (int i = 0; key[i] != '\0'; i++) {
        hash = (hash + key[i]) % TABLE_SIZE;
    }
    return hash;
}

// 创建哈希表
HashTable* createHashTable() {
    HashTable* ht = (HashTable*)malloc(sizeof(HashTable));
    for (int i = 0; i < TABLE_SIZE; i++) {
        ht->table[i] = NULL; // 初始化每个槽位为空链表
    }
    return ht;
}

// 插入键值对到哈希表
void insert(HashTable* ht, char* key, int value) {
    int index = hash(key);
    KeyValuePair* kvp = (KeyValuePair*)malloc(sizeof(KeyValuePair));
    kvp->key = strdup(key);
    kvp->value = value;
    kvp->next = NULL;

    // 检查该位置是否已经存在节点
    KeyValuePair* curr = ht->table[index];
    KeyValuePair* prev = NULL;
    while (curr != NULL) {
        if (strcmp(curr->key, key) == 0) {
            // 键已经存在，更新值并返回
            curr->value = value;
            free(kvp->key); // 释放键的内存，因为键已经存在
            free(kvp); // 释放键值对的内存
            return;
        }
        prev = curr;
        curr = curr->next;
    }

    // 如果该位置为空，则直接将键值对插入
    if (prev == NULL) {
        ht->table[index] = kvp;
    } else { // 否则，将键值对添加到链表末尾
        prev->next = kvp;
    }
}

// 查找键对应的值
int find(HashTable* ht, char* key) {
    int index = hash(key);
    KeyValuePair* curr = ht->table[index];
    while (curr != NULL) {
        if (strcmp(curr->key, key) == 0) {
            return curr->value;
        }
        curr = curr->next;
    }
    return -1; // 没有找到
}

// 销毁哈希表
void destroyHashTable(HashTable* ht) {
    for (int i = 0; i < TABLE_SIZE; i++) {
        KeyValuePair* curr = ht->table[i];
        while (curr != NULL) {
            KeyValuePair* temp = curr;
            curr = curr->next;
            free(temp->key);
            free(temp);
        }
    }
    free(ht);
}

int main() {
    HashTable* ht = createHashTable();

    insert(ht, "apple", 5);
    insert(ht, "banana", 10);
    insert(ht, "orange", 15);
    insert(ht, "grape", 20);
    insert(ht, "apple", 25); // 重复键，将会形成链表

    printf("apple: %d\n", find(ht, "apple"));
    printf("banana: %d\n", find(ht, "banana"));
    printf("orange: %d\n", find(ht, "orange"));
    printf("grape: %d\n", find(ht, "grape"));

    destroyHashTable(ht);

    return 0;
}