Reversing a doubly linked list
main.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Node {
int x;
struct Node* next;
struct Node* prev;
} Node;
void deallocate(Node** tail, Node** head) {
if (*tail == NULL) {
return;
}
Node* curr = *tail;
while (curr->next != NULL) {
curr = curr->next;
free(curr->prev);
}
free(curr);
*tail = NULL;
*head = NULL;
}
void insert_beginning(Node** tail, Node** head, int value) {
Node* new_node = malloc(sizeof(Node));
if (new_node == NULL) {
exit(1);
return;
}
new_node->x = value;
new_node->prev = NULL;
new_node->next = *tail;
(*tail)->prev = new_node;
*tail = new_node;
}
void insert_end(Node** tail, Node** head, int value) {
Node* new_node = malloc(sizeof(Node));
if (new_node == NULL) {
exit(3);
return;
}
new_node->x = value;
new_node->next = NULL;
new_node->prev = *head
(*head)->next = new_node;
*head = new_node;
}
void init(Node** tail, Node** head, int value) {
Node* new_node = malloc(sizeof(int));
if (new_node == NULL) {
exit(2);
return;
}
new_node->x = value;
new_node->prev = NULL;
new_node->next = NULL;
*tail = new_node;
*head = new_node;
}
void remove_node(Node* node) {
if (node->prev != NULL) {
node->prev->next = node->next;
}
if (node->next != NULL) {
node->next->prev = node->prev;
}
free(node);
}
Node* find_node(Node* tail, int value) {
for (Node* curr = tail; curr != NULL; curr = curr->next) {
if (curr->x == value) {
return curr;
}
}
return NULL;
}
Node* find_node_recursive(Node* node, int value) {
if (node == NULL) {
return NULL;
}
if (node->x == value) {
return node;
}
return find_node_recursive(node->next, value);
}
void reverse(Node** tail, Node** head) {
Node* curr = *tail;
while (curr != NULL) {
Node* next = curr->next;
curr->next = curr->prev;
curr->prev = next;
curr = next;
}
Node* aux = *tail;
*tail = *head;
*head = aux;
}
int main(int argc, char* argv[]) {
Node* tail = NULL;
Node* head = NULL;
init(&tail, &head, 7);
insert_beginning(&tail, 3);
insert_beginning(&tail, 1);
insert_end(&head, 1);
reverse(&tail, &head);
for (Node* curr = tail; curr != NULL; curr = curr->next) {
printf("%d ", curr->x);
}
deallocate(&tail, &head);
return 0;
}
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