#include <stdio.h>
#include <stdlib.h>
struct Node {
  int data;
  struct Node *next;
  struct Node *prev;
};
struct Node *createSLL(int value) {
  struct Node *newNode = (struct Node *)malloc(sizeof(struct Node));
  newNode->data = value;
  newNode->next = NULL;
  newNode->prev = NULL;
  return newNode;
}
void addAtBeginning(struct Node **head, int value) {
  struct Node *newNode = createSLL(value);
  newNode->next = *head;
  if (*head != NULL) {
    (*head)->prev = newNode;
  }
  *head = newNode;
}
void addAtEnd(struct Node **head, int value) {
  struct Node *newNode = createSLL(value);
  struct Node *curr = *head;
  while (curr->next != NULL) {
    curr = curr->next;
  }
  curr->next = newNode;
  newNode->prev = curr;
}
void addAtIntermediate(struct Node *prevNode, int value) {
  if (prevNode == NULL) {
    printf("Clouldn't add. The given node doesn't exist.\n");
    return;
  }
  struct Node *newNode = createSLL(value);
  newNode->next = prevNode->next;
  if (prevNode->next != NULL) {
    prevNode->next->prev = newNode;
  }
  newNode->prev = prevNode;
  prevNode->next = newNode;
}
void deleteFromBeginning(struct Node **head) {
  if (*head == NULL) {
    printf("List is empty!\n");
    return;
  }
  struct Node *temp = *head;
  *head = (*head)->next;
  if (*head != NULL) {
    (*head)->prev = NULL;
  }
  free(temp);
}
void deleteFromEnd(struct Node **head) {
  if (*head == NULL) {
    printf("List is Empty.\n");
    return;
  }
  struct Node *curr = *head;
  while (curr->next != NULL) {
    curr = curr->next;
  }
  if (curr->prev != NULL) {
    curr->prev->next = NULL;
  } else {
    *head = NULL;
  }
  free(curr);
}
void deleteFromIntermediate(struct Node **head, struct Node *toDel) {
  if (*head == NULL || toDel == NULL) {
    printf("Clouldn't delete. The given node doesn't exixt.\n");
    return;
  }
  if (*head == toDel) {
    *head = (*head)->next;
  }
  if (toDel->next != NULL) {
    toDel->next->prev = toDel->prev;
  }
  if (toDel->prev != NULL) {
    toDel->prev->next = toDel->next;
  }
  free(toDel);
}
void displaySLL(struct Node *head) {
  struct Node *curr = head;
  printf("NULL <-> ");
  while (curr != NULL) {
    printf("%d <-> ", curr->data);
    curr = curr->next;
  }
  printf("NULL\n");
}
int main() {
  struct Node *head = NULL;
  int choise, value, prevValue;
  do {
    printf("<--:: MAIN MENU ::-->\n1. Add At Beginning\n2. Add At End\n3. "
           "Display DLL\n4. Add At Intermediate\n5. Delete from Beginning\n6. "
           "Delete From End\n7. Delete from Intermediate\n0. Exit\n\nENTER "
           "YOUR CHOISE ::-->> ");
    scanf("%d", &choise);
    switch (choise) {
    case 1:
      printf("Enter the value: ");
      scanf("%d", &value);
      addAtBeginning(&head, value);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 2:
      printf("Enter the value: ");
      scanf("%d", &value);
      addAtEnd(&head, value);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 3:
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 4:
      printf("Enter the value to be added: ");
      scanf("%d", &value);
      printf("Enter the value after which you want to add: ");
      scanf("%d", &prevValue);
      struct Node *curr = head;
      while (curr->data != prevValue) {
        curr = curr->next;
      }
      struct Node *prevNode = curr;
      addAtIntermediate(prevNode, value);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 5:
      deleteFromBeginning(&head);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 6:
      deleteFromEnd(&head);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
      break;
    case 7:
      printf("Enter the value to be deleted: ");
      scanf("%d", &value);
      struct Node *curr2 = head;
      while (curr2->data != value) {
        curr2 = curr2->next;
      }
      struct Node *toDel = curr2;
      deleteFromIntermediate(&head, toDel);
      printf("CURRENT LINKED LIST\n");
      displaySLL(head);
    case 0:
      break;
    default:
      printf("Invalid Choise! Try Again.\n");
      break;
    }
  } while (choise != 0);
}