Solution: The Payment Processor

#include <iostream>
#include <vector>
#include <variant>
#include <algorithm>
struct CreditCard {};
struct BankTransfer {};
using PaymentMethod = std::variant<CreditCard, BankTransfer>;
enum class Status {
    Pending,
    Processed
};
constexpr double CC_FEE_RATE = 0.02;
struct Transaction {
    double amount;
    PaymentMethod method;
    Status status;
};
int main() {
    std::vector<Transaction> transactions = {
        {100.0, CreditCard{}, Status::Pending},
        {200.0, BankTransfer{}, Status::Pending},
        {50.0, CreditCard{}, Status::Pending}
    };
    // Process transactions
    std::for_each(transactions.begin(), transactions.end(), [](Transaction& t) {
        // Apply fee only if it is a CreditCard
        if (std::holds_alternative<CreditCard>(t.method)) {
            t.amount += (t.amount * CC_FEE_RATE);
        }
        
        // Update status using the scoped enum
        t.status = Status::Processed;
    });
    // Output results
    for (const auto& t : transactions) {
        std::cout << "Amount: " << t.amount 
                  << " | Status: " << (t.status == Status::Processed ? "Processed" : "Pending") 
                  << "\n";
    }
    return 0;
}