I create a case 02 for calculate the bill. function is running but the problem is when the output is coming as a 0. that's problem in my code. Further Information's I cannot find where is the error coming from I changed variables also but it not correct that way. I think calculation is correct problem's is value is always shown in the console is 0.

我创建了一个用于计算账单的案例02。函数正在运行，但问题是当输出为0时。这就是我的代码中的问题。进一步的信息我找不到错误是从哪里来的，我也改变了变量，但不能以这种方式更正。我认为计算是正确的，问题的is值总是在控制台中显示为0。

This is the code,

这就是密码，

case 2: { // Create Bill
    clearScreen();
    cout << "****** CREATE BILL ******" << endl;

    // Prompt user for customer name and invoice ID
    string customerName;
    string invoiceID;

    cout << "Enter Customer Name: ";
    cin.ignore();
    getline(cin, customerName);

    cout << "Enter Invoice ID: ";
    cin >> invoiceID;

    // Display menu for choosing bill type
    clearScreen();
    cout << "Choose Bill Type:" << endl;
    cout << "1. Bakery Item Bill" << endl;
    cout << "2. Package Bill" << endl;
    cout << "\n****************" << endl;
    cout << "Enter your choice: ";
    int billType;
    cin >> billType;

    // Initialize variables to store bill details
    double totalBill = 0.0;
    string billContents = "";

    if (billType == 1) { // Bakery Item Bill
        clearScreen();
        ifstream bakeryFile("bakery_items.txt");
        if (!bakeryFile.is_open()) {
            cout << "Data Base Error" << endl;
            return; 
        }

        
        vector<string> selectedItems;
        vector<int> selectedQuantities;
       
        string line;
        while (getline(bakeryFile, line)) {
            cout << line << endl;
        }

        bakeryFile.close();

        // Prompt user to select items and quantities
        char addMoreItems;
        do {
            string selectedItem;
            int quantity;

            cout << "\nEnter the Item ID of the bakery item you want to add: ";
            cin >> selectedItem;

            // Validate if the selected item exists
            ifstream bakeryFile("bakery_items.txt");
            string bakeryLine;
            bool itemFound = false;
            while (getline(bakeryFile, bakeryLine)) {
                stringstream ss(bakeryLine);
                string itemID, itemName, itemCategory;
                double itemPrice;

                ss >> itemID >> itemName >> itemCategory >> itemPrice;

                if (itemID == selectedItem) {
                    itemFound = true;
                    cout << "Enter the quantity: ";
                    cin >> quantity;

                    // Validate if the quantity is valid
                    if (quantity <= 0) {
                        cout << "Please enter a positive quantity." << endl;
                        continue;
                    }

                    double subtotal = itemPrice * quantity;
                    totalBill += subtotal;

                    // Append bill details for the selected item to billContents
                    billContents += "Item ID: " + itemID + " | Item Name: " + itemName + " | Quantity: " + to_string(quantity) + " | Subtotal: " + to_string(subtotal) + " GBP\n";

                    break;
                }
            }

            if (!itemFound) {
                cout << "Please enter a valid Bakery Item ID." << endl;
            }

            cout << "Do you want to add more items? (Y/N): ";
            cin >> addMoreItems;
        } while (addMoreItems == 'Y' || addMoreItems == 'y');
    }
    else if (billType == 2) { // Package Bill
        clearScreen();
        ifstream packageFile("packages.txt");
        if (!packageFile.is_open()) {
            cout << "Data Base Error" << endl;
            return;
        }

        // Initialize vector to store selected packages
        vector<string> selectedPackages;

        string line;
        while (getline(packageFile, line)) {
            cout << line << endl;
        }

        packageFile.close();

        // Prompt user to select packages
        char addMorePackages;
        do {
            string selectedPackage;

            cout << "\nEnter the Package ID you want to add: ";
            cin >> selectedPackage;

            // Validate if the selected package exists
            ifstream packageFile("packages.txt");
            string packageLine;
            bool packageFound = false;
            while (getline(packageFile, packageLine)) {
                stringstream ss(packageLine);
                string packageID, packageName;
                double packagePrice;

                ss >> packageID >> packageName >> packagePrice;

                if (packageID == selectedPackage) {
                    packageFound = true;

                    double subtotal = packagePrice;
                    totalBill += subtotal; // Add the subtotal to the totalBill

                    // Append bill details for the selected package to billContents
                    billContents += "Package ID: " + packageID + " | Package Name: " + packageName + " | Subtotal: " + to_string(subtotal) + " GBP\n";

                    break;
                }
            }

            if (!packageFound) {
                cout << "Please enter a valid Package ID." << endl;
            }

            cout << "Do you want to add more packages? (Y/N): ";
            cin >> addMorePackages;
        } while (addMorePackages == 'Y' || addMorePackages == 'y');
    }
    else {
        cout << "Invalid choice. Exiting..." << endl;
        return; 
    }

    // Display the final bill
    clearScreen();
    cout << "\n****** FINAL BILL ******" << endl;
    cout << "Customer Name: " << customerName << endl;
    cout << "Invoice ID: " << invoiceID << endl;
    cout << "Bill Type: " << (billType == 1 ? "Bakery Item Bill" : "Package Bill") << endl;
    cout << "------------------------" << endl;
    cout << billContents;
    cout << "\n------------------------" << endl;
    cout << "Total Bill (GBP): " << totalBill << endl;

    // Ask the user if they want to save the bill
    char saveBillChoice;
    cout << "\nDo you want to save the bill? (Y/N): ";
    cin >> saveBillChoice;

    if (saveBillChoice == 'Y' || saveBillChoice == 'y') {
     
        ofstream billFile("bills.txt", ios::app);
        if (billFile.is_open()) {
            billFile << "Customer Name: " << customerName << endl;
            billFile << "Invoice ID: " << invoiceID << endl;
            billFile << "Bill Type: " << (billType == 1 ? "Bakery Item Bill" : "Package Bill") << endl;
            billFile << "------------------------" << endl;
            billFile << billContents;
            billFile << "Total Bill (GBP): " << totalBill << endl;
            billFile << "========================" << endl;
            billFile.close();
            cout << "\n------------------------" << endl;
            cout << "Bill saved successfully." << endl;
            cout << "------------------------" << endl;
        }
        else {
            cout << "Could not save the bill." << endl;
        }
    }
    else {
        cout << "\n[x] Bill not saved." << endl;
    }
    break;
}

I want to fix that calculation issue in this code.

我想修复此代码中的计算问题。