c++ you just need to modify the doublelink list flie,please make sure it can run and finsih these methods

\} template Type ListType: : back( ) const \{ assert(tail != NULL); //confirm tail exists return tail->data; //return the data of the tail node \} template void ListType>: :copyList (const ListType> \& otherList) \{ NodeType *newNode; //pointer to create a node NodeType current; //pointer to traverse the list if (head != NULL) //if the list is nonempty, make it empty destroyList(); if (otherList. head == NULL) //otherList is empty \{ head = NULL; tail = NULL; count =0; \} else \{ current = otherList. head; // current points to the count = otherList . count; // list to be copied //copy the head node head = new NodeType ; / / create the node head->data = current > data; // copy the data head->next = NULL; // set the link field of tail = head; // the node to NULL // the next node //copy the remaining list while (current != NULL) \{ newNode = new NodeType ;// create a node newNode > data = current > data; // copy the data newNode->next = NULL; // set the link of // newNode to NULL tail->next = newNode; //attach newNode after tail tail = newNode; // make tail point to //the actual tail node current = current > next; 1/ make current point //to the next node \}/ /end while \}/lend else \}//end copylist