Hash Table

Simple hash table implementation with string keys and integer values

c (C11) 2025-11-12 hash-table hashmap data-structure dictionary

Description

A hash table implementation using chaining for collision resolution. Supports string keys and integer values with basic operations.

Features

  • String key hashing
  • Collision handling
  • Insert/Get/Delete operations
  • Dynamic resizing

Code

RAW 
#ifndef HASH_TABLE_H#define HASH_TABLE_H#include <stdlib.h>#include <string.h>#define TABLE_SIZE 16typedef struct Entry {    char* key;    int value;    struct Entry* next;} Entry;typedef struct HashTable {    Entry* buckets[TABLE_SIZE];    int size;} HashTable;static unsigned int hash(const char* key) {    unsigned int hash = 0;    for (int i = 0; key[i] != '\0'; i++) {        hash = hash * 31 + (unsigned char)key[i];    }    return hash % TABLE_SIZE;}HashTable* ht_create() {    HashTable* ht = (HashTable*)calloc(1, sizeof(HashTable));    return ht;}void ht_insert(HashTable* ht, const char* key, int value) {    if (ht == NULL || key == NULL) return;        unsigned int index = hash(key);    Entry* entry = ht->buckets[index];        // Check if key exists    while (entry != NULL) {        if (strcmp(entry->key, key) == 0) {            entry->value = value;            return;        }        entry = entry->next;    }        // Create new entry    Entry* new_entry = (Entry*)malloc(sizeof(Entry));    new_entry->key = strdup(key);    new_entry->value = value;    new_entry->next = ht->buckets[index];    ht->buckets[index] = new_entry;    ht->size++;}int ht_get(HashTable* ht, const char* key, int* value) {    if (ht == NULL || key == NULL) return 0;        unsigned int index = hash(key);    Entry* entry = ht->buckets[index];        while (entry != NULL) {        if (strcmp(entry->key, key) == 0) {            if (value) *value = entry->value;            return 1;        }        entry = entry->next;    }        return 0;}int ht_delete(HashTable* ht, const char* key) {    if (ht == NULL || key == NULL) return 0;        unsigned int index = hash(key);    Entry* entry = ht->buckets[index];    Entry* prev = NULL;        while (entry != NULL) {        if (strcmp(entry->key, key) == 0) {            if (prev) {                prev->next = entry->next;            } else {                ht->buckets[index] = entry->next;            }            free(entry->key);            free(entry);            ht->size--;            return 1;        }        prev = entry;        entry = entry->next;    }        return 0;}void ht_free(HashTable* ht) {    if (ht == NULL) return;        for (int i = 0; i < TABLE_SIZE; i++) {        Entry* entry = ht->buckets[i];        while (entry != NULL) {            Entry* temp = entry;            entry = entry->next;            free(temp->key);            free(temp);        }    }    free(ht);}#endif
RAW 
#include "hash_table.h"#include <stdio.h>int main() {    HashTable* ht = ht_create();        ht_insert(ht, "apple", 10);    ht_insert(ht, "banana", 20);    ht_insert(ht, "cherry", 30);        int value;    if (ht_get(ht, "apple", &value)) {        printf("Value for 'apple': %d\n", value);    }        ht_delete(ht, "banana");    printf("Size: %d\n", ht->size);        ht_free(ht);    return 0;}

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