Add mandatory tasks

Author: hackerSa3edy

0x1A-hash_tables/.gitignore

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+*.o
+.vscode/*
+tests.c

0x1A-hash_tables/0-hash_table_create.c

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+#include "hash_tables.h"
+
+/**
+ * hash_table_create - creates a hash table.
+ *
+ * @size: Size of the array.
+ *
+ * Return: pointer to a hash table, NULL otherwise.
+*/
+hash_table_t *hash_table_create(unsigned long int size)
+{
+	hash_table_t *hash_table = malloc(sizeof(hash_node_t));
+	unsigned int index;
+
+	if (hash_table == NULL)
+		return (NULL);
+
+	hash_table->size = size;
+	hash_table->array = malloc(sizeof(hash_node_t *) * size);
+	if (hash_table->array == NULL)
+	{
+		free(hash_table);
+		return (NULL);
+	}
+
+	for (index = 0; index < size; index++)
+		hash_table->array[index] = NULL;
+
+	return (hash_table);
+}

0x1A-hash_tables/0-main.c

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+#include "hash_tables.h"
+
+/**
+ * main - check the code for
+ *
+ * Return: Always EXIT_SUCCESS.
+ */
+int main(void)
+{
+    hash_table_t *ht;
+
+    ht = hash_table_create(1024);
+    printf("%p\n", (void *)ht);
+    return (EXIT_SUCCESS);
+}

0x1A-hash_tables/1-djb2.c

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+#include "hash_tables.h"
+
+/**
+ * hash_djb2 - hash function (djb2 algorithm)
+ *
+ * @str: The key to be hashed
+ *
+ * Return: The hash
+*/
+unsigned long int hash_djb2(const unsigned char *str)
+{
+	unsigned long int hash;
+	int c;
+
+	hash = 5381;
+	while ((c = *str++))
+	{
+		hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
+	}
+	return (hash);
+}

0x1A-hash_tables/1-main.c

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+#include "hash_tables.h"
+
+/**
+ * main - check the code
+ *
+ * Return: Always EXIT_SUCCESS.
+ */
+int main(void)
+{
+    char *s;
+
+    s = "cisfun";
+    printf("%lu\n", hash_djb2((unsigned char *)s));
+    s = "Don't forget to tweet today";
+    printf("%lu\n", hash_djb2((unsigned char *)s));
+    s = "98";
+    printf("%lu\n", hash_djb2((unsigned char *)s));
+    return (EXIT_SUCCESS);
+}

0x1A-hash_tables/100-sorted_hash_table.c

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+# Project: 0x1A. C - Hash tables
+
+## Resources
+
+#### Read or watch:
+
+* [What is a HashTable Data Structure - Introduction to Hash Tables , Part 0](https://intranet.alxswe.com/rltoken/IQVfdxJlS6jhAgcuUoCseg)
+* [Hash function](https://intranet.alxswe.com/rltoken/ZKpRI_FxOxAz80Onpfy0Ew)
+* [Hash table](https://intranet.alxswe.com/rltoken/mxjKpEfAw3E5B8S3inPuHQ)
+* [All about hash tables](https://intranet.alxswe.com/rltoken/3RwwAqmpGJpMiBa7BE9fAQ)
+* [why hash tables and not arrays](https://intranet.alxswe.com/rltoken/OgO7uga3PIaCTMtTzYCY3g)
+## Learning Objectives
+
+### General
+
+* What is a hash function
+* What makes a good hash function
+* What is a hash table, how do they work and how to use them
+* What is a collision and what are the main ways of dealing with collisions in the context of a hash table
+* What are the advantages and drawbacks of using hash tables
+* What are the most common use cases of hash tables
+## Tasks
+
+| Task | File |
+| ---- | ---- |
+| 0. >>> ht = {} | [0-hash_table_create.c](./0-hash_table_create.c) |
+| 1. djb2 | [1-djb2.c](./1-djb2.c) |
+| 2. key -> index | [2-key_index.c](./2-key_index.c) |
+| 3. >>> ht['betty'] = 'cool' | [3-hash_table_set.c](./3-hash_table_set.c) |
+| 4. >>> ht['betty'] | [4-hash_table_get.c](./4-hash_table_get.c) |
+| 5. >>> print(ht) | [5-hash_table_print.c](./5-hash_table_print.c) |
+| 6. >>> del ht | [6-hash_table_delete.c](./6-hash_table_delete.c) |
+| 7. $ht['Betty'] = 'Cool' | [100-sorted_hash_table.c](./100-sorted_hash_table.c) |

0x1A-hash_tables/2-key_index.c

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+#ifndef HASH_TABLES
+#define HASH_TABLES
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * struct hash_node_s - Node of a hash table
+ *
+ * @key: The key, string
+ * The key is unique in the HashTable
+ * @value: The value corresponding to a key
+ * @next: A pointer to the next node of the List
+ */
+typedef struct hash_node_s
+{
+	char *key;
+	char *value;
+	struct hash_node_s *next;
+} hash_node_t;
+
+/**
+ * struct hash_table_s - Hash table data structure
+ *
+ * @size: The size of the array
+ * @array: An array of size @size
+ * Each cell of this array is a pointer to the first node of a linked list,
+ * because we want our HashTable to use a Chaining collision handling
+ */
+typedef struct hash_table_s
+{
+	unsigned long int size;
+	hash_node_t **array;
+} hash_table_t;
+
+hash_table_t *hash_table_create(unsigned long int size);
+unsigned long int hash_djb2(const unsigned char *str);
+
+
+#endif /* HASH_TABLES */