[C] Doubly Circular Linked List기반의 ADT List 연산 구현

c++의 구조체를 이용해서 직접 Doubly Circular Linked List를 구현해봤다

구현한 총 연산은 create, traversal, insert(first, middle, last), delete(first, middle, last)

typedef struct Node {
	int data;
	struct Node* next;
	struct Node* prev;
}Node;

void create(Node* head) {
	head = NULL;
}

void traversal(Node* head) {
	Node* cur = head;
	if (head == NULL)return;
	do {
		printf("%d ", cur->data);
		cur = cur->next;
	} while (cur!= head);
	printf("\n");
}

Node* insertFirst(Node* head, int data) {
	Node* node = (Node*)malloc(sizeof(Node));
	node->data = data;
	if (head == NULL) {
		node->next = node;
		node->prev = node;
	}
	else {
		node->next = head;
		node->prev = head->prev;
		head->prev->next = node;
		head->prev = node;
	}
	head = node;
	return head;
}

Node* insertLast(Node* head, int data) {
	Node* node = (Node*)malloc(sizeof(Node));
	node->data = data;
	if (head == NULL) {
		node->next = node;
		node->prev = node;
		head = node;
	}
	else {
		node->next = head;
		node->prev = head->prev;
		head->prev->next = node;
		head->prev = node;
	}
	return head;
}

Node* insert(Node* head, int data, int pos) {
	Node* node = (Node*)malloc(sizeof(Node));
	node->data = data;
	
	Node* pre = head,*next;
	for (size_t i = 0; i < pos-1; i++)
		pre = pre->next;

	node->prev = pre;
	node->next = pre->next;

	pre->next->prev = node;
	pre->next = node;

	return head;	
}

Node* deleteFirst(Node* head) {
	if (head == NULL)return NULL;

	head->next->prev = head->prev;
	head->prev->next = head->next;

	Node* node = head;
	head = head->next;
	free(node);

	return head;
}

Node* delete(Node* head,int pos) {
	if (head == NULL)return NULL;

	Node* pre = head;
	for (size_t i = 0; i < pos - 1; i++)
		pre = pre->next;

	Node* node = pre->next;
	node->next->prev = pre;
	pre->next = node->next;

	free(node);

	return head;
}

Node* deleteLast(Node* head) {
	if (head == NULL)return NULL;

	Node* pre = head->prev->prev;
	Node* cur = pre->next;

	Node* node = cur;
	pre->next = cur->next;
	cur->next->prev = pre;

	free(node);

	return head;
}

코드만 보고는 헷갈렸는데 그림 그려가면서 순서를 정리하니까 감이 잡힌다

고민의 흔적