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feat: add Circular Doubly Linked List implementation (#1038)

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* Create circular_doubly_linked_list.c

* Update data_structures/linked_list/circular_doubly_linked_list.c

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* Update circular_doubly_linked_list.c

Added brief description of library files

* Update data_structures/linked_list/circular_doubly_linked_list.c

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* Update data_structures/linked_list/circular_doubly_linked_list.c

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* Update circular_doubly_linked_list.c

Done the all suggested changes.

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

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* Update circular_doubly_linked_list.c

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* There was typo while calling delete_first_node !

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: David Leal <halfpacho@gmail.com>

* updating DIRECTORY.md

* Suggested changes are done.

Done the suggested changes in functions 
1. delete_first_node() 
2. delete_last_node()

* updating DIRECTORY.md

* updating DIRECTORY.md

* Worked on Suggested Changes

* Suggested changes are done.

* Update circular_doubly_linked_list.c

Worked on all the suggested changes.

Co-Authored-By: David Leal <halfpacho@gmail.com>
Co-Authored-By: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>
Co-Authored-By: Taj <tjgurwara99@users.noreply.github.com>

* updating DIRECTORY.md

* updating DIRECTORY.md

* Worked on suggested changes for test cases.

Check the code's functionality [here](https://leetcode.com/playground/WcRBMWa8)

Co-Authored-By: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>

* updating DIRECTORY.md

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>

* Update circular_doubly_linked_list.c

Update: Worked on suggested changes.

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>

* Update data_structures/linked_list/circular_doubly_linked_list.c

Co-authored-by: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>

* Worked on suggested changes.

* Minor upgrade.

* updating DIRECTORY.md

---------

Co-authored-by: David Leal <halfpacho@gmail.com>
Co-authored-by: github-actions[bot] <github-actions@users.noreply.github.com>
Co-authored-by: CascadingCascade <122662061+CascadingCascade@users.noreply.github.com>
Co-authored-by: Taj <tjgurwara99@users.noreply.github.com>
This commit is contained in:
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@ -86,6 +86,7 @@
* [Min Heap](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/heap/min_heap.c)
* Linked List
* [Ascending Priority Queue](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/linked_list/ascending_priority_queue.c)
* [Circular Doubly Linked List](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/linked_list/circular_doubly_linked_list.c)
* [Circular Linked List](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/linked_list/circular_linked_list.c)
* [Doubly Linked List](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/linked_list/doubly_linked_list.c)
* [Merge Linked Lists](https://github.com/TheAlgorithms/C/blob/HEAD/data_structures/linked_list/merge_linked_lists.c)

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data_structures/linked_list/circular_doubly_linked_list.c Normal file
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/**
* @file
*
* @details
* Circular [Doubly Linked
* List](https://en.wikipedia.org/wiki/Doubly_linked_list) combines the
* properties of a doubly linked list and a circular linked list in which two
* consecutive elements are linked or connected by the previous. Next, the
* pointer and the last node point to the first node via the next pointer, and
* the first node points to the last node via the previous pointer.
*
* In this implementation, functions to insert at the head, insert at the last
* index, delete the first node, delete the last node, display list, and get
* list size functions are coded.
*
* @author [Sahil Kandhare](https://github.com/SahilK-027)
*
*/
#include <assert.h> /// to verify assumptions made by the program and print a diagnostic message if this assumption is false.
#include <inttypes.h> /// to provide a set of integer types with universally consistent definitions that are operating system-independent
#include <stdio.h> /// for IO operations
#include <stdlib.h> /// for including functions involving memory allocation such as `malloc`
/**
* @brief Circular Doubly linked list struct
*/
typedef struct node
{
struct node *prev, *next; ///< List pointers
uint64_t value; ///< Data stored on each node
} ListNode;
/**
* @brief Create a list node
* @param data the data that the node initialises with
* @return ListNode* pointer to the newly created list node
*/
ListNode *create_node(uint64_t data)
{
ListNode *new_list = (ListNode *)malloc(sizeof(ListNode));
new_list->value = data;
new_list->next = new_list;
new_list->prev = new_list;
return new_list;
}
/**
* @brief Insert a node at start of list
* @param head start pointer of list
* @param data the data that the node initialises with
* @return ListNode* pointer to the newly created list node
* inserted at the head
*/
ListNode *insert_at_head(ListNode *head, uint64_t data)
{
if (head == NULL)
{
head = create_node(data);
return head;
}
else
{
ListNode *temp;
ListNode *new_node = create_node(data);
temp = head->prev;
new_node->next = head;
head->prev = new_node;
new_node->prev = temp;
temp->next = new_node;
head = new_node;
return head;
}
}
/**
* @brief Insert a node at end of list
*
* @param head start pointer of list
* @param data the data that the node initialises with
* @return ListNode* pointer to the newly added list node that was
* inserted at the head of list.
*/
ListNode *insert_at_tail(ListNode *head, uint64_t data)
{
if (head == NULL)
{
head = create_node(data);
return head;
}
else
{
ListNode *temp1, *temp2;
ListNode *new_node = create_node(data);
temp1 = head;
temp2 = head->prev;
new_node->prev = temp2;
new_node->next = temp1;
temp1->prev = new_node;
temp2->next = new_node;
return head;
}
}
/**
* @brief Function for deletion of the first node in list
*
* @param head start pointer of list
* @return ListNode* pointer to the list node after deleting first node
*/
ListNode *delete_from_head(ListNode *head)
{
if (head == NULL)
{
printf("The list is empty\n");
return head;
}
ListNode *temp1, *temp2;
temp1 = head;
temp2 = temp1->prev;
if (temp1 == temp2)
{
free(temp2);
head = NULL;
return head;
}
temp2->next = temp1->next;
(temp1->next)->prev = temp2;
head = temp1->next;
free(temp1);
return head;
}
/**
* @brief Function for deletion of the last node in list
*
* @param head start pointer of list
* @return ListNode* pointer to the list node after deleting first node
*/
ListNode *delete_from_tail(ListNode *head)
{
if (head == NULL)
{
printf("The list is empty\n");
return head;
}
ListNode *temp1, *temp2;
temp1 = head;
temp2 = temp1->prev;
if (temp1 == temp2)
{
free(temp2);
head = NULL;
return head;
}
(temp2->prev)->next = temp1;
temp1->prev = temp2->prev;
free(temp2);
return head;
}
/**
* @brief The function that will return current size of list
*
* @param head start pointer of list
* @return int size of list
*/
int getsize(ListNode *head)
{
if (!head)
{
return 0;
}
int size = 1;
ListNode *temp = head->next;
while (temp != head)
{
temp = temp->next;
size++;
}
return size;
}
/**
* @brief Display list function
* @param head start pointer of list
* @returns void
*/
void display_list(ListNode *head)
{
printf("\nContents of your linked list: ");
ListNode *temp;
temp = head;
if (head != NULL)
{
while (temp->next != head)
{
printf("%" PRIu64 " <-> ", temp->value);
temp = temp->next;
}
if (temp->next == head)
{
printf("%" PRIu64, temp->value);
}
}
else
{
printf("The list is empty");
}
printf("\n");
}
/**
* @brief access the list by index
* @param list pointer to the target list
* @param index access location
* @returns the value at the specified index,
* wrapping around if the index is larger than the size of the target
* list
*/
uint64_t get(ListNode *list, const int index)
{
if (list == NULL || index < 0)
{
exit(EXIT_FAILURE);
}
ListNode *temp = list;
for (int i = 0; i < index; ++i)
{
temp = temp->next;
}
return temp->value;
}
/**
* @brief Self-test implementations
* @returns void
*/
static void test()
{
ListNode *testList = NULL;
unsigned int array[] = {2, 3, 4, 5, 6};
assert(getsize(testList) == 0);
printf("Testing inserting elements:\n");
for (int i = 0; i < 5; ++i)
{
display_list(testList);
testList = insert_at_head(testList, array[i]);
assert(testList->value == array[i]);
assert(getsize(testList) == i + 1);
}
printf("\nTesting removing elements:\n");
for (int i = 4; i > -1; --i)
{
display_list(testList);
assert(testList->value == array[i]);
testList = delete_from_head(testList);
assert(getsize(testList) == i);
}
printf("\nTesting inserting at tail:\n");
for (int i = 0; i < 5; ++i)
{
display_list(testList);
testList = insert_at_tail(testList, array[i]);
assert(get(testList, i) == array[i]);
assert(getsize(testList) == i + 1);
}
printf("\nTesting removing from tail:\n");
for (int i = 4; i > -1; --i)
{
display_list(testList);
testList = delete_from_tail(testList);
assert(getsize(testList) == i);
// If list is not empty, assert that accessing the just removed element
// will wrap around to the list head
if (testList != NULL)
{
assert(get(testList, i) == testList->value);
}
else
{
// If the list is empty, assert that the elements were removed after
// the correct number of iterations
assert(i == 0);
}
}
}
/**
* @brief Main function
* @returns 0 on exit
*/
int main()
{
test(); // run self-test implementations
return 0;
}