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Doubly linked list, simple code. (#673)

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* Doubly linked list, simple code.

#633

* organizing code a bit more

* add link in DIRECTORY.md and more comments/cleaning.

* remove global variables and redundancy.

* add Wikipedia reference

* add documentation comments in all functions/headers

* add update in file brief

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>

* remove part of file @details

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
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DIRECTORY.md
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@ -71,6 +71,7 @@
* Linked List
* [Ascendingpriorityqueue](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/ascendingpriorityqueue.c)
* [Circular Linked List](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/circular_linked_list.c)
* [Doubly Linked List](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/doubly_linked_list.c)
* [Merge Linked Lists](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/merge_linked_lists.c)
* [Middle Element In List](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/middle_element_in_list.c)
* [Queue Linked List](https://github.com/TheAlgorithms/C/blob/master/data_structures/linked_list/queue_linked_list.c)

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data_structures/linked_list/doubly_linked_list.c Normal file
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/**
* @file
* @brief Implementation of [Doubly linked list](https://en.wikipedia.org/wiki/Doubly_linked_list)
* @details
* A doubly linked list is a data structure with a sequence
* of components called nodes. Within that nodes there are
* three elements: a value recorded, a pointer to the next
* node, and a pointer to the previous node.
*
* In this implementation, the functions of creating the list,
* inserting by position, deleting by position, searching
* for value, printing the list, and an example of how the
* list works were coded.
*
* @author [Gabriel Mota Bromonschenkel Lima](https://github.com/GabrielMotaBLima)
*/
#include <stdio.h>
#include <stdlib.h>
/**
* @brief Doubly linked list struct
*/
typedef struct list
{
double value; ///< value saved on each node
struct list *next, *prev; ///< directing to other nodes or NULL
} List;
/**
* @brief Create list function, a new list containing one node will be created
* @param value a value to be saved into the first list node
* @returns new_list the list created
*/
List *create(double value);
/**
* @brief Insertion by position into the list function
* @param list a doubly linked List
* @param value a value to be inserted into the list
* @param pos a position into the list for value insertion
* @returns list the input list with a node more or the same list
*/
List *insert(List *list, double value, int pos);
/**
* @brief Deletion by position into the list function
* @param list a doubly linked List
* @param pos a position into the list for value Deletion
* @returns list the input list with deleted values or the same list
*/
List *delete(List *list, int pos);
/**
* @brief Search value into the list function
* @param list a doubly linked list
* @param value a value to be looked for into the list
* @returns `1` if the looked up value exists
* @returns `0` if the looked up value doesn't exist
*/
int search(List *list, double value);
/**
* @brief Print list function
* @param list a doubly linked List
* @returns void
*/
void print(List *list);
/**
* @brief Example function
* @returns void
*/
void example();
/**
* @brief Main function
* @returns 0 on exit
*/
int main()
{
// examples for better understanding
example();
// code here
return 0;
}
/**
* @brief Create list function, a new list containing one node will be created
* @param value a value to be saved into the first list node
* @returns new_list the list created
*/
List *create(double value)
{
List *new_list = (List *)malloc(sizeof(List));
new_list->value = value;
new_list->next = NULL;
new_list->prev = NULL;
return new_list;
}
/**
* @brief Insertion by position into the list function
* @param list a doubly linked List
* @param value a value to be inserted into the list
* @param pos a position into the list for value insertion
* @returns list the input list with a node more or the same list
*/
List *insert(List *list, double value, int pos)
{
// list NULL case
if (list == NULL)
{
list = create(value);
return list;
}
// position existing case
if (pos > 0)
{
List *cpy = list, *tmp = cpy;
int flag = 1, index = 1, size = 0;
while (tmp != NULL)
{
size++;
tmp = tmp->next;
}
// first position case
if (pos == 1)
{
List *new_node = create(value);
new_node->next = cpy;
cpy->prev = new_node;
list = new_node;
return list;
}
// position existing in list range case
if (size + 2 > pos)
{
while (cpy->next != NULL && index < pos)
{
flag++;
index++;
cpy = cpy->next;
}
List *new_node = (List *)malloc(sizeof(List));
new_node->value = value;
// position into list with no poiting for NULL
if (flag == pos)
{
cpy->prev->next = new_node;
new_node->next = cpy;
new_node->prev = cpy->prev;
cpy->prev = new_node;
}
// last position case
if (flag < pos)
{
new_node->next = cpy->next;
new_node->prev = cpy;
cpy->next = new_node;
}
}
return list;
}
}
/**
* @brief Deletion by position into the list function
* @param list a doubly linked List
* @param pos a position into the list for value Deletion
* @returns list the input list with deleted values or the same list
*/
List *delete(List *list, int pos)
{
// list NULL case
if (list == NULL)
return list;
// position existing case
if (pos > 0)
{
List *cpy = list, *tmp = cpy;
int flag = 1, index = 1, size = 0;
while (tmp != NULL)
{
size++;
tmp = tmp->next;
}
// first position case
if (pos == 1)
{
if (size == 1)
return NULL;
cpy = cpy->next;
cpy->prev = NULL;
return cpy;
}
// position existing in list range case
if (size + 2 > pos)
{
while (cpy->next != NULL && index < pos)
{
flag++;
index++;
cpy = cpy->next;
}
if (flag == pos)
{
// position into list with no poiting for NULL
if (cpy->next != NULL)
{
cpy->prev->next = cpy->next;
cpy->next->prev = cpy->prev;
}
// last position case
else
cpy->prev->next = NULL;
}
}
return list;
}
}
/**
* @brief Search value into the list function
* @param list a doubly linked list
* @param value a value to be looked for into the list
* @returns `1` if the looked up value exists
* @returns `0` if the looked up value doesn't exist
*/
int search(List *list, double value)
{
if (list == NULL)
return 0;
if (list->value == value)
return 1;
search(list->next, value);
}
/**
* @brief Print list function
* @param list a doubly linked List
* @returns void
*/
void print(List *list)
{
if (list != NULL)
{
printf("%f\t", list->value);
print(list->next);
}
}
/**
* @brief Example function
* @returns void
*/
void example()
{
List *my_list = NULL;
double node_value = 0;
int searching;
my_list = create(node_value);
my_list = insert(my_list, 3, 1);
my_list = insert(my_list, 5, 3);
my_list = insert(my_list, 10, 3);
my_list = insert(my_list, 20, 3);
print(my_list);
searching = search(my_list, 20);
printf("\n%d\n", searching);
my_list = delete (my_list, 1);
my_list = delete (my_list, 1);
my_list = delete (my_list, 1);
my_list = delete (my_list, 1);
print(my_list);
searching = search(my_list, 20);
printf("\n%d\n", searching);
}