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#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;
}
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