c语言实现哈希表数据结构

哈希表的数据结构:

其实就是数组+链表：如图，

     通过一个hash函数将key转化成数组的下标，如果对应的下标在数组里面有数据，那么就冲突了，冲突了怎么办呢，这个时候就把这个数组当成链表的头结点，然后通过头插法或者尾插法将新的节点数据插入到这个链表里面，理论上有hash表的size有多大，就有多少条链表，上图就有16条，冲突得越多，链表的长度就越大。由于查找key的时候，通过key算出对应的数组下标，这个计算的过程是hash算法实现的，一般时间复杂度为O(1)，所以得到下标的时间复杂度是O(1)， 通过下标在数组中找数据的时间复杂度也是O(1)， 所以哈希表的查找的时间复杂度在没有冲突的情况下是O(1), 一旦有冲突，那么就要遍历链表了。这个时候的时间复杂度就是根据链表的长度来决定的。

       通过上面的数据结构，能够定义出每个hash节点的数据结构

typedef struct HashNode{
    char *key;                 
    int value;
    struct HashNode *nextNode;
}HashNode;

      而哈希表即上面HashNode的数组

typedef struct HashTable{
    HashNode * hashNode[MAX_TABLE_SIZE];
    int currentIndex;
}HashTable;

　　好了，我们的数据结构构造出来了之后，接下来就是，初始化，添加，查找，删除，等一系列操作hash表的骚操作了

　　

---

 初始化:

void InitHashTable(HashTable *hashTable)
{
    memset(hashTable->hashNode, 0, sizeof(HashNode *) * MAX_TABLE_SIZE);
    hashTable->currentIndex = 0;
}

---

插入函数：

//插入key value
void Insert(HashTable *hashTable, char *key, int value)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode * newNode = (HashNode *)malloc(sizeof(HashNode));
    newNode->nextNode = NULL;
    newNode->key = (char *)malloc(sizeof(char) * (strlen(key) + 1));
    strcpy(newNode->key, key);
    newNode->key[strlen(key)] = '';
    newNode->value = value;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明没有冲突
        hashTable->hashNode[pos] = newNode;
        hashTable->currentIndex++;
        return;
    }
    //头结点不为空，同时头结点的key和输入的key相同，覆盖value
    if (strcmp(p->key, key) == 0) {
        p->value = value;
        return;
    }

    //头结点不为空，冲突，插入到链表的第二个节点
    HashNode *q = p->nextNode;
    newNode->nextNode = q;
    p->nextNode = newNode;
}

---

获取key对应的value

int * Get(HashTable *hashTable, char *key)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明不存在这样的key
        return NULL;
    } else {
        HashNode *q = p;
        while (q != NULL) {
            if(strcmp(q->key, key) == 0) {
                return &(q->value);
            }
            q = q->nextNode;
        }
        return NULL;
    }
}

---

删除对应的key

int Drop(HashTable *hashTable, char *key)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明不存在这样的key
        return 0;
    }
    else {
        if(strcmp(p->key, key) == 0) {  //删除的如果是头结点
            hashTable->hashNode[pos] = p->nextNode;
            free(p->key);
            free(p);
            return 1;
        }
        //删除的不是头结点的情况
        HashNode *q = p->nextNode;
        HashNode * last = p;
        while (q != NULL) {
            if(strcmp(q->key, key) == 0) {
                last->nextNode = q->nextNode;
                free(q->key);
                free(q);
                return 1;
            }
            last = q;
            q = q->nextNode;
        }
        return 0;
    }
}

---

打印所有数据

void PrintHashTable(HashTable *hashTable)
{
    for(int i = 0; i < MAX_TABLE_SIZE; i++) {
        HashNode *head = hashTable->hashNode[i];
        if (head == NULL)
            continue;
        printf("
数组下标:%d======>", i);
        printf("(%s:%d)", head->key, head->value);
        head = head->nextNode;
        while(head) {
            printf("-->(%s:%d)", head->key, head->value);
            head = head->nextNode;
        }
    }
}

---

释放堆内存

void ClearHashTable(HashTable* hashTable)
{
    for(int i = 0; i < MAX_TABLE_SIZE; i++) {
        HashNode *head = hashTable->hashNode[i];
        while(head) {
            HashNode *temp = head->nextNode;
            free(head->key);
            free(head);
            head = temp;
        }
    }
}

---

哈希规则

unsigned long HashFun(const char *key)
{
    unsigned long hash = 0;
    int len = strlen(key);
    for (int i = 0; i < len; i++) {
        hash = hash * 33 + key[i];
    }
    return hash;
}

---

main函数测试

int main(void)
{
    HashTable *hashTable = (HashTable *)malloc(sizeof(HashTable));
    InitHashTable(hashTable);
    Insert(hashTable,"1234", 1);
    Insert(hashTable,"11234", 1);
    Insert(hashTable,"hello", 2);
    Insert(hashTable,"world", 3);
    Insert(hashTable,"hzp", 4);
    Insert(hashTable,"java", 5);
    Insert(hashTable,"b", 12);
    Insert(hashTable,"c", 12);
    Insert(hashTable,"c1", 12);
    Insert(hashTable,"c++", 18);
    Insert(hashTable,"html", 18);
    Insert(hashTable,"web", 18);
    Insert(hashTable,"python", 56);
    PrintHashTable(hashTable);
    int *data = Get(hashTable,"b");
    printf("
====%d=====
", *data);
    Drop(hashTable, "python");
    PrintHashTable(hashTable);
    ClearHashTable(hashTable);

}

运行截图：

 附代码：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_KEY_LEN 100
#define MAX_TABLE_SIZE 1000

typedef struct HashNode{
    char *key;
    int value;
    struct HashNode *nextNode;
}HashNode;


typedef struct HashTable{
    HashNode * hashNode[MAX_TABLE_SIZE];
    int currentIndex;
}HashTable;


unsigned long HashFun(const char *key)
{
    unsigned long hash = 0;
    int len = strlen(key);
    for (int i = 0; i < len; i++) {
        hash = hash * 33 + key[i];
    }
    return hash;
}
//初始化
void InitHashTable(HashTable *hashTable)
{
    memset(hashTable->hashNode, 0, sizeof(HashNode *) * MAX_TABLE_SIZE);
    hashTable->currentIndex = 0;
}

//插入key value
void Insert(HashTable *hashTable, char *key, int value)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode * newNode = (HashNode *)malloc(sizeof(HashNode));
    newNode->nextNode = NULL;
    newNode->key = (char *)malloc(sizeof(char) * (strlen(key) + 1));
    strcpy(newNode->key, key);
    newNode->key[strlen(key)] = '';
    newNode->value = value;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明没有冲突
        hashTable->hashNode[pos] = newNode;
        hashTable->currentIndex++;
        return;
    }
    //头结点不为空，同时头结点的key和输入的key相同，覆盖value
    if (strcmp(p->key, key) == 0) {
        p->value = value;
        return;
    }

    //头结点不为空，冲突，插入到链表的第二个节点
    HashNode *q = p->nextNode;
    newNode->nextNode = q;
    p->nextNode = newNode;
}

int * Get(HashTable *hashTable, char *key)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明不存在这样的key
        return NULL;
    } else {
        HashNode *q = p;
        while (q != NULL) {
            if(strcmp(q->key, key) == 0) {
                return &(q->value);
            }
            q = q->nextNode;
        }
        return NULL;
    }
}

int Drop(HashTable *hashTable, char *key)
{
    int pos = HashFun(key) % MAX_TABLE_SIZE;
    HashNode *p = hashTable->hashNode[pos];
    if (p == NULL) {  //如果头结点为空，说明不存在这样的key
        return 0;
    }
    else {
        if(strcmp(p->key, key) == 0) {  //删除的如果是头结点
            hashTable->hashNode[pos] = p->nextNode;
            free(p->key);
            free(p);
            return 1;
        }
        //删除的不是头结点的情况
        HashNode *q = p->nextNode;
        HashNode * last = p;
        while (q != NULL) {
            if(strcmp(q->key, key) == 0) {
                last->nextNode = q->nextNode;
                free(q->key);
                free(q);
                return 1;
            }
            last = q;
            q = q->nextNode;
        }
        return 0;
    }
}


void ClearHashTable(HashTable* hashTable)
{
    for(int i = 0; i < MAX_TABLE_SIZE; i++) {
        HashNode *head = hashTable->hashNode[i];
        while(head) {
            HashNode *temp = head->nextNode;
            free(head->key);
            free(head);
            head = temp;
        }
    }
}

void PrintHashTable(HashTable *hashTable)
{
    for(int i = 0; i < MAX_TABLE_SIZE; i++) {
        HashNode *head = hashTable->hashNode[i];
        if (head == NULL)
            continue;
        printf("
index:%d======>", i);
        printf("(%s:%d)", head->key, head->value);
        head = head->nextNode;
        while(head) {
            printf("-->(%s:%d)", head->key, head->value);
            head = head->nextNode;
        }
    }
}

int main(void)
{
    HashTable *hashTable = (HashTable *)malloc(sizeof(HashTable));
    InitHashTable(hashTable);
    Insert(hashTable,"1234", 1);
    Insert(hashTable,"11234", 1);
    Insert(hashTable,"hello", 2);
    Insert(hashTable,"world", 3);
    Insert(hashTable,"hzp", 4);
    Insert(hashTable,"java", 5);
    Insert(hashTable,"b", 12);
    Insert(hashTable,"c", 12);
    Insert(hashTable,"c1", 12);
    Insert(hashTable,"c++", 18);
    Insert(hashTable,"html", 18);
    Insert(hashTable,"web", 18);
    Insert(hashTable,"python", 56);
    PrintHashTable(hashTable);
    int *data = Get(hashTable,"b");
    printf("
====%d=====
", *data);
    Drop(hashTable, "python");
    PrintHashTable(hashTable);
    ClearHashTable(hashTable);

}