Below is my code in C++. This code is done using the singly linked list data structure. I need you to only add one more thing in this code. Make a login system function which requires a username and password to enter the program. If the username and password is not correct, then the rest of the program should not start. You can only use singly linked list data structure.

#include #include #include using namespace std; struct Data { string name, city, symptoms, immune_level, severity; int admit_no, age; }; struct Node { Data data; Node* next; }; Node* append(Node* head, Data data) { Node* temp = new Node; temp->data = data; temp->next = NULL; if (head == NULL) { head = temp; return head; } Node* last = head; while (last->next != NULL) { last = last->next; } last->next = temp; cout << "Append completed" << endl; return head; } void update(Node* head, string data, string newData) { while (head != NULL) { if (head->data.name == data) { head->data.name = newData; break; } head = head->next; } } int listLength(Node* head) { int temp = 0; if (head == NULL) { cout << "Node is empty" << endl; return 0; } while (head->next != NULL) { ++temp; head = head->next; } return temp + 1; } void deletee(Node* head, int loc) { Node* temp = new Node; temp = head; if (head == NULL) {

cout << "Node is null" << endl; return; } for (int i = 1; i <= loc; ++i) { temp = temp->next; if (i < loc) { head = head->next; } } head->next = temp->next; } Node* search(Node* head, string v) { if (head == NULL) { cout << "Node is empty returning null" << endl; return NULL; } int l = 1; while (head->next != NULL && head->data.name != v) { head = head->next; ++l; } cout << "Element found at location " << l << endl; return head; } void printLinkedList(Node* head) { if (head == NULL) { cout << "Head is null" << endl; return; } while (head->next != NULL) { cout << "Name: " << head->data.name << ", City: " << head->data.city << ", Immune Level: " << head->data.immune_level << ", Symptoms: " << head->data.symptoms << ", Severity: " << head->data.severity << ", Age: " << head->data.age << ", Admit No: " << head->data.admit_no << endl; head = head->next; } cout << "Name: " << head->data.name << ", City: " << head->data.city << ", Immune Level: " << head->data.immune_level << ", Symptoms: " << head->data.symptoms << ", Severity: " << head->data.severity << ", Age: " << head->data.age << ", Admit No: " << head->data.admit_no << endl; } void filewrite(Node * head) { ofstream fout; fout.open("patients.txt"); while (head->next != NULL) { fout << "Name: " << head->data.name << ", City: " << head->data.city << ", Immune Level: " << head->data.immune_level << ", Symptoms: " << head->data.symptoms << ", Severity: " << head->data.severity << ", Age: " << head->data.age << ", Admit No: " << head->data.admit_no << endl; head = head->next; } fout << "Name: " << head->data.name << ", City: " << head->data.city << ", Immune Level: " << head->data.immune_level << ", Symptoms: " << head->data.symptoms << ", Severity: " << head->data.severity << ", Age: " << head->data.age << ", Admit No: " << head->data.admit_no << endl; fout.close(); } Data inputPatients() { string name, city, symptoms, immune_level, severity; int admit_no, age; Data p; cout << "Enter Patient Name: "; cin.ignore(); getline(cin, name); cout << "Enter Patient City: "; getline(cin, city); cout << "Enter Patient Symptoms: "; getline(cin, symptoms); cout << "Enter Patient Immune Level: "; getline(cin, immune_level); cout << "Enter patient Severity: "; getline(cin, severity); cout << "Enter Patient Admit No.: "; cin >> admit_no; cout << "Enter Patient Age: "; cin >> age; p.name = name; p.city = city; p.symptoms = symptoms; p.immune_level = immune_level; p.severity = severity; p.admit_no = admit_no; p.age = age; cout << "Completed input operation" << endl; return p; } int main() { Node* head = NULL; Data patient; string nameToSearch; string oldName, newName; int op; cout << " 1-Add Patient 2-Delete Patient(Must have 3 patients in hospital to delete patients.) 3-Search by Name 4-Total Patients in Hospital 5-Print All Patients Record 6-Update Patient Name 7-Save Records in a file 8-Exit" << endl; while (cin >> op) { switch (op) { case 1: cout << "Enter Patient Details Below" << endl; patient = inputPatients(); head = append(head, patient); break; case 2: if (listLength(head) < 2) { cout << "Length is less then two. Terminating program" << endl; exit(1); } else { cout << "Enter location where you want to delete a patient"; int l; cin >> l; deletee(head, l - 1); } break; case 3: cout << "Enter name to search patient: "; cin.ignore(); getline(cin, nameToSearch); search(head, nameToSearch); break; case 4: cout << "You have " << listLength(head) << " Patients in your Hospital." << endl; break; case 5: printLinkedList(head); break; case 6: cin.ignore(); cout << "Enter old name "; getline(cin, oldName); cout << "Enter New Name "; getline(cin, newName); update(head, oldName, newName); break; case 8: exit(0); case 7: filewrite(head); break; default: cout << "Wrong option Selected" << endl; } cout << " 1-Add Patient 2-Delete Patient(Must have 3 patients in hospital to delete patients.) 3-Search by Name 4-Total Patients in Hospital 5-Print All Patients Record 6-Update Patient Name 7-Save Records in a file 8-Exit" << endl; } }