1st one

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;

int main(){
	int quantity,counter,product_choice,payment_option,time,i;
	double product_cost,delivery_charge,discount,surcharge,final_cost,card_cost;
	string username,password,date,loyalty,card_choice,choice;
	string product[499]={"Wireless Earphones","iPhone 11","USB Type C charging cable","iPhone Case","Sony PS4","Microsoft Surface Go","Logitech G403 Mouse","Portable Phone Tripod","CCTV Camera","HP Inkjet Printer","HP Original Ink Cartridge x4","Waterproof Outdoor Sleeping Bag","Multipurpose Hiking Backpack","Foldable Treadmill Running Machine","Stationary Exercise Bike","Dove Body Wash","Head & Shoulders Shampoo","LED Wall Clock","Elba Pressure Cooker","Thermos 1.0L","Electronic Kitchen Scale","10pcs Dish Cloth Towel","Non-stick Frying Pan"};
	const int price[499]={35.00,3599.00,12.50,10.00,1449.00,2899.00,168.99,14.99,115.00,189.00,25.00,18.90,59.99,669.00,124.50,20.00,15.90,24.90,230.00,31.00,12.50,11.99,89.00};
	cout<<"Welcome to Lapeeza, here are the products we have,\n";
	for (i=0;i<23;i++){
		cout<<i+1<<". "<<product[i]<<" - RM"<<price[i]<<endl;
    }
	cout<<endl;
	do{
	cout<<"Which product would you like to buy? Use the number of the product to choose : ";
	cin>>product_choice;
	while(product_choice>23||product_choice<1){
		cout<<"Please make a valid choice : ";
		cin>>product_choice;
	}
	cout<<"How many units would you like? : ";
	cin>>quantity;
	counter=counter+quantity;
	product_cost=price[product_choice-1]*quantity;
	final_cost=final_cost+product_cost;
	cout<<"Would you like to buy another product?(y/n) : ";
	cin>>choice;
	} while (choice=="Y"||choice=="y");


	if (counter<6&&counter>0){
		delivery_charge=5;
	}
	else if (counter>5&&counter<11){
		delivery_charge=6;
	}
	else if (counter>10&&counter<16){
		delivery_charge=6.50;
	}
	else {
		delivery_charge=0;
	}

    cout<<"\n4 payment options are available on Lapeeza.\n";
	do{
		cout<<"\n1) Cash on delivery (2% charge applies)\n";
		cout<<"2) Credit or debit card (2% charge applies)\n";
		cout<<"3) Lapeeza wallet (enjoy 5% discount on all products)\n";
		cout<<"4) Online banking\n";
		cout<<"Please choose a payment option : ";
		cin>>payment_option;
	}   while (payment_option>4||payment_option<1);
	if (payment_option==1||payment_option==2){
		surcharge=0.02;
	}
	else if (payment_option=3){
		discount=0.05;
	}


	cout<<"\nAlright, we just need a few more details to calculate your final cost.\n";
	cout<<"Please enter your username : ";
	cin>>username;
	cout<<"Please enter your password : ";
	cin>>password;
	cout<<"You are now logged in. \n";
	cout<<"Do you own a loyalty card or have spent at least RM5 on Lapeeza for three days straight?(y/n)  : ";
	cin>>loyalty;
	if (loyalty!="y"&&loyalty!="Y"&&loyalty!="n"&&loyalty!="N"){
		cout<<"Please enter a valid option (y/n) : ";
		cin>>loyalty;
	}
	if (loyalty=="n"||loyalty=="N"){
		cout<<"Do you want to purchase a loyalty card for RM10 to enjoy a 10% cash rebate for your purchases? (y/n) : ";
		cin>>card_choice;
		if (card_choice=="y"||card_choice=="Y"){
			card_cost=10;
		}
	}
	if (loyalty=="y"||loyalty=="Y"||card_choice=="y"||card_choice=="Y"){
		discount=discount+0.1;
	}
	cout<<"What is today's date? (dd/mm) : ";
	cin>>date;
	cout<<"What is the time? (0000~2359) : ";
	cin>>time;
	if (date.substr(0,2)=="13"){
		if (time<=200||time>=1300){
			discount=discount+0.2;
		}
	}
	final_cost=final_cost+delivery_charge+card_cost+(surcharge*final_cost)-(discount*final_cost);
	cout<<fixed<<setprecision(2)<<"\nThank you for shopping with Lapeeza!\nYour final cost is RM"<<final_cost<<".\n";
}