#include using namespace std; class Node { public: int data; Node *prev; Node *next; }; void printList(Node*); void insertAtHead(Node *&head_ref, int new_data){ Node* new_node = new Node(); new_node->data = new_data; new_node->prev = NULL; new_node->next = head_ref; if(head_ref != NULL){ head_ref->prev = new_node; } head_ref = new_node; } void insertAtEnd(Node* &head_ref, int new_data){ Node* tail = head_ref; Node *new_node = new Node(); new_node->data = new_data; new_node->next = NULL; if(head_ref == NULL){ new_node->prev = NULL; head_ref = new_node; return; } // traverse to the last node while(tail->next != NULL){ tail = tail->next; } tail->next = new_node; new_node->prev = tail; } void insertAfter(Node* prev_node, int new_data){ if(prev_node == NULL){ cout<< "prev node can not be null"; return; } Node* new_node = new Node(); new_node->data = new_data; new_node->next = prev_node->next; new_node->prev = prev_node; prev_node->next = new_node; if(new_node->next != NULL) new_node->next->prev = new_node; } void insertBefore(Node* &head_ref, Node* next_node, int new_data){ if(next_node == NULL){ cout << "next node can not be null."; return; } Node* new_node = new Node(); new_node->data = new_data; new_node->prev = next_node->prev; new_node->next = next_node; next_node->prev = new_node; if(new_node->prev != NULL){ new_node->prev->next = new_node; } else { head_ref = new_node; } } int main() { Node* head = NULL; for(int i=1; i<=5; i++){ insertAtHead(head, i); } printList(head); for(int i=1; i<=5; i++){ insertAtEnd(head, i); } printList(head); insertAfter(head->next->next, 4); printList(head); insertBefore(head, head->next->next, 7); printList(head); return 0; } void printList(Node *node) { cout << "\nPrinting list: "; while (node != NULL) { cout << node->data << " "; node = node->next; } cout << endl; }

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