#include <stdio.h>
#include <stdlib.h>

struct node {
	int val;
	struct node *prev;
	struct node *next;
};

struct node *head;
struct node *tail;
int len = 0;

void
prepend(int val)
{
	struct node *tmp = malloc(sizeof(struct node));
	tmp->val = val;
	if (head == NULL) {
		head = tail = tmp;
		return;
	}
	tmp->val = val;
	tmp->next = head;
	head->prev = tmp;
	head = tmp;
	++len;
}

void
append(int val)
{
	struct node *tmp = malloc(sizeof(struct node));
	tmp->val = val;
	if (!tail) {
		head = tail = tmp;
		return;
	}
	tmp->prev = tail;
	tail->next = tmp;
	tail = tmp;
	++len;
}

struct node
*get_at(int i)
{
	struct node *cur = head;
	for (int j = 0; cur && j < i; ++j) {
		cur = cur->next;
	}
	return cur;
}

void
insert_at(int val, int i)
{
	if (i > len) {
		printf("index is greater than the list length\n");
	} else if (i == len) {
		append(val);
		return;
	} else if (i == 0) {
		prepend(val);
		return;
	}
	struct node *cur = get_at(i);
	struct node *tmp = malloc(sizeof(struct node));
	tmp->next = cur;
	tmp->prev = cur->prev;
	cur->prev = tmp;

	if (tmp->prev) {
		tmp->prev->next = tmp;
	}
	++len;
}

int
remove_node(struct node *tmp)
{
	--len;
	if (len == 0) {
		head = tail = NULL;
		return -1;
	}

	if (tmp->prev) {
		tmp->prev->next = tmp->next;
	}
	if (tmp->next) {
		tmp->next->prev = tmp->prev;
	}

	if (tmp == head) {
		head = tmp->next;
	}
	if (tmp == tail) {
		tail = tmp->prev;
	}

	int val = tmp->val;
	free(tmp);
	return val;
}

int
remove_val(int val)
{
	struct node *cur = head;
	for (int i = 0; cur && cur->val != val && i < len; ++i) {
		cur = cur->next;
	}
	if (!cur) {
		return -1;
	}
	return remove_node(cur);
}

int
remove_at(int i)
{
	struct node *tmp = get_at(i);
	if (!tmp) {
		return -1;
	}
	return remove_node(tmp);
}

int
get(int i)
{
	get_at(i)->val;
}

void
print()
{
	struct node *cur = head;
	while (cur != NULL) {
		printf("%d ", cur->val);
		cur = cur->next;
	}
	printf("\n");
}

int
main()
{
	int val, n = 0;
	printf("How many integers?\n");
	scanf("%d", &n);
	for (int i = 0; i < n; ++i) {
		printf("Enter an integer \n");
		scanf("%d", &val);
		prepend(val);
		print();
	}

	return 0;
}