How to create a hash table in the C language?

In C language, a hash table can be created by following these steps:

1. Create a structure for a hash table with two members: a fixed-size array to store data, and a flag array to indicate whether each position in the array has data. For instance:

#define SIZE 10

typedef struct {
    int data[SIZE];
    int flags[SIZE];
} HashTable;

1. Initialize the hash table by setting all elements in the array and flag array to their initial values (e.g. 0).

void initializeHashTable(HashTable* hashTable) {
    int i;
    for(i = 0; i < SIZE; i++) {
        hashTable->data[i] = 0;
        hashTable->flags[i] = 0;
    }
}

1. Implement a hash function that maps the data to be inserted to a position in the hash table. Common hash functions include division hashing, multiplication hashing, square mid-digits, and more. For example, here is a simple division hashing method:

int hashFunction(int key) {
    return key % SIZE;
}

1. Implement the insertion operation, inserting data into the corresponding position in the hash table. If that position already has data, use a conflict resolution strategy (such as linear probing, quadratic probing, separate chaining, etc.) to find the next available position.

void insert(HashTable* hashTable, int key) {
    int index = hashFunction(key);
    while(hashTable->flags[index] != 0) {
        index = (index + 1) % SIZE; // 线性探测法
    }
    hashTable->data[index] = key;
    hashTable->flags[index] = 1;
}

1. Perform a search operation by finding the corresponding data in the hash table based on the given keyword.

int search(HashTable* hashTable, int key) {
    int index = hashFunction(key);
    while(hashTable->flags[index] != 0) {
        if(hashTable->data[index] == key) {
            return index;
        }
        index = (index + 1) % SIZE;
    }
    return -1; // 表示未找到
}

This way, a simple hash table can be created. In practical applications, it can be resized or deleted as needed.