going through an example of hash table

c/hash-table-pro.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <string.h>
+
+typedef struct item {
+    char *key;
+    int   value;
+} item;
+
+item *linear_search(item *items, size_t size, const char *key) {
+    for (size_t i = 0; i < size; i++) {
+        if (strcmp(items[i].key, key) == 0) {
+            return (&items[i]);
+        }
+    }
+
+    return (NULL);
+}
+
+int main() {
+    item items[] = {
+        {"foo", 10},
+        {"bar", 20},
+        {"hello", 30},
+        {"x", 40}};
+
+    size_t total_items = sizeof(items) / sizeof(items);
+
+    item *found = linear_search(items, total_items, "foo");
+
+    if (found == NULL) {
+        printf("linear search: value of 'foo' has no key\n");
+        return (1);
+    }
+
+    printf("linear search: value of 'foo' is: %d", found->value);
+    return (0);
+}

c/hash-table.c

@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct HashTable {
+    char *data[16];
+} HashTable;
+
+HashTable *new_hashtable() {
+    HashTable *ht = malloc(sizeof(HashTable));
+    for (int i = 0; i < 16; i++) {
+        ht->data[i] = NULL;
+    }
+
+    return (ht);
+}
+
+int get_index_for_letter(char letter) {
+    if (letter >= 'a' && letter <= 'z') {
+        return (letter - 'a') + 1;
+    } else {
+        return -1;
+    }
+}
+
+int hash(char *word) {
+    int word_len = strlen(word);
+    int accum = 1;
+    int index;
+    for (int i = 0; i < word_len; i++) {
+        index = get_index_for_letter(word[i]);
+        accum *= index;
+    }
+
+    return accum % 16;
+}
+
+char *get(HashTable *h, char *key) {
+    int hash_val = hash(key);
+    return h->data[hash_val];
+}
+
+void insert(HashTable *h, char *key, char *value) {
+    int hashed_key = hash(key);
+
+    if (h->data[hashed_key] != NULL) {
+        fprintf(stderr, "ERROR: collision!");
+        exit(1);
+    }
+
+    h->data[hashed_key] = value;
+}
+
+void delete(HashTable *h, char *key) {
+    int hashed_key = hash(key);
+    h->data[hashed_key] = NULL;
+}
+
+int main() {
+    HashTable *hash_table = new_hashtable();
+    char      *key = "hello";
+    insert(hash_table, key, "world");
+    insert(hash_table, "hlleo", "world");
+    char *res = get(hash_table, "hello");
+
+    printf("the value at key '%s' is '%s'", key, res);
+
+    return 0;
+}