Ниже приведены программы на языке C, реализующие двустороннюю очередь (абстрактный тип данных) с использованием массива и двусвязного списка.

1. Двусторонняя очередь с использованием массива:

   #include <stdio.h>
   #define MAX_SIZE 100
   int dequeue[MAX_SIZE];
   int front = -1;
   int rear = -1;
   void insertFront(int item) {
   if ((front == 0 && rear == MAX_SIZE - 1) || (front == rear + 1)) {
       printf("Queue is full.\n");
       return;
   } else if (front == -1 && rear == -1) {
       front = rear = 0;
   } else if (front == 0) {
       front = MAX_SIZE - 1;
   } else {
       front--;
   }
   dequeue[front] = item;
   printf("Item %d inserted at the front.\n", item);
   }
   void insertRear(int item) {
   if ((front == 0 && rear == MAX_SIZE - 1) || (front == rear + 1)) {
       printf("Queue is full.\n");
       return;
   } else if (front == -1 && rear == -1) {
       front = rear = 0;
   } else if (rear == MAX_SIZE - 1) {
       rear = 0;
   } else {
       rear++;
   }
   dequeue[rear] = item;
   printf("Item %d inserted at the rear.\n", item);
   }
   void deleteFront() {
   if (front == -1 && rear == -1) {
       printf("Queue is empty.\n");
       return;
   } else if (front == rear) {
       printf("Item %d deleted from the front.\n", dequeue[front]);
       front = rear = -1;
   } else if (front == MAX_SIZE - 1) {
       printf("Item %d deleted from the front.\n", dequeue[front]);
       front = 0;
   } else {
       printf("Item %d deleted from the front.\n", dequeue[front]);
       front++;
   }
   }
   void deleteRear() {
   if (front == -1 && rear == -1) {
       printf("Queue is empty.\n");
       return;
   } else if (front == rear) {
       printf("Item %d deleted from the rear.\n", dequeue[rear]);
       front = rear = -1;
   } else if (rear == 0) {
       printf("Item %d deleted from the rear.\n", dequeue[rear]);
       rear = MAX_SIZE - 1;
   } else {
       printf("Item %d deleted from the rear.\n", dequeue[rear]);
       rear--;
   }
   }
   void display() {
   if (front == -1 && rear == -1) {
       printf("Queue is empty.\n");
       return;
   }
   printf("Queue elements: ");
   int i = front;
   while (i != rear) {
       printf("%d ", dequeue[i]);
       if (i == MAX_SIZE - 1) {
           i = 0;
       } else {
           i++;
       }
   }
   printf("%d\n", dequeue[i]);
   }
   int main() {
   insertFront(5);
   insertRear(10);
   insertFront(3);
   display();
   deleteFront();
   display();
   deleteRear();
   display();
   
   return 0;
   }

2. Двусторонняя очередь с использованием двусвязного списка:

   #include <stdio.h>
   #include <stdlib.h>
   struct Node {
   int data;
   struct Node* prev;
   struct Node* next;
   };
   struct Node* front = NULL;
   struct Node* rear = NULL;
   void insertFront(int item) {
   struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
   newNode->data = item;
   newNode->prev = NULL;
   newNode->next = front;
   if (front == NULL) {
       front = rear = newNode;
   } else {
       front->prev = newNode;
       front = newNode;
   }
   printf("Item %d inserted at the front.\n", item);
   }
   void insertRear(int item) {
   struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
   newNode->data = item;
   newNode->prev = rear;
   newNode->next = NULL;
   if (rear == NULL) {
       front = rear = newNode;
   } else {
       rear->next = newNode;
       rear = newNode;
   }
   printf("Item %d inserted at the rear.\n", item);
   }
   void deleteFront() {
   if (front == NULL && rear == NULL) {
       printf("Queue is empty.\n");
       return;
   } else if (front == rear) {
       printf("Item %d deleted from the front.\n", front->data);
       free(front);
       front = rear = NULL;
   } else {
       struct Node* temp = front;
       printf("Item %d deleted from the front.\n", temp->data);
       front = front->next;
       front->prev = NULL;
       free(temp);
   }
   }
   void deleteRear() {
   if (front == NULL && rear == NULL) {
       printf("Queue is empty.\n");
       return;
   } else if (front == rear) {
       printf("Item %d deleted from the rear.\n", rear->data);
       free(rear);
       front = rear = NULL;
   } else {
       struct Node* temp = rear;
       printf("Item %d deleted from the rear.\n", temp->data);
       rear = rear->prev;
       rear->next = NULL;
       free(temp);
   }
   }
   void display() {
   if (front == NULL && rear == NULL) {
       printf("Queue is empty.\n");
       return;
   }
   printf("Queue elements: ");
   struct Node* current = front;
   while (current != NULL) {
       printf("%d ", current->data);
       current = current->next;
   }
   printf("\n");
   }
   int main() {
   insertFront(5);
   insertRear(10);
   insertFront(3);
   display();
   deleteFront();
   display();
   deleteRear();
   display();
   
   return 0;
   }