Parallel Arrays in C++ - c++

Question

Trying to create a program that takes a coffee flavor add-in and checks if it's valid using an array.
If valid it uses the array index to gather price information.
I managed to write the code below, but it only works for 1 iteration.
How can alter it so a user can enter: Cream and cinnamon and output the total of each add-in as well as the total price of the cup of coffee? The cup of coffee starts with a base price of $2.00
#include <iostream>
#include <string>
using namespace std;
int main()
{
// Declare variables.
string addIn; // Add-in ordered
const int NUM_ITEMS = 5; // Named constant
// Initialized array of add-ins
string addIns[] = { "Cream", "Cinnamon", "Chocolate", "Amaretto", "Whiskey" };
// Initialized array of add-in prices
double addInPrices[] = { .89, .25, .59, 1.50, 1.75 };
bool foundIt = false; // Flag variable
int x; // Loop control variable
double orderTotal = 2.00; // All orders start with a 2.00 charge
string QUIT = "XXX";
// Get user input
cout << "Enter coffee add-in or XXX to quit: ";
cin >> addIn;
// Write the rest of the program here.
for (x = 0; x < NUM_ITEMS && foundIt == false && addIn != QUIT; x++) {
if (addIn == addIns[x]) {
foundIt = true;
x--;
}
}
if (foundIt == true) {
cout << addIns[x] << " $" << addInPrices[x] <<endl;
cout << "$" << orderTotal + addInPrices[x] <<endl;
}
else {
cout << "Sorry, we do not carry that." <<endl;
cout << "Order total is $ " << orderTotal <<endl;
}
return 0;
}

Answer 1

Don't use parallel arrays - you will mess up maintaining them.
Better options:
Create a struct for your add-ins:
struct Addin {
std::string name;
double price;
}
and use an array (or better yet an std::vector) of those structs.
Another option is to use a map:
std::map<std::string, double> addIns = {
{"Cream", .89},
{"Cinnamon", .25},
// etc.
};
Then you won't need a loop, just a lookup
auto item = addIns.find(addIn);
if(item != addIns.end() {
// do your math here
}

Answer 2

Your program is written to get a single output. For multiple outputs there have to be loops and the not found condition also has to be re-written.
try this
#include <iostream>
#include <string>
using namespace std;
int main()
{
// Declare variables.
const int NUM_ITEMS = 5; // Named constant
string addIn[NUM_ITEMS]; // Add-in ordered
// Initialized array of add-ins
string addIns[] = { "Cream", "Cinnamon", "Chocolate", "Amaretto", "Whiskey" };
// Initialized array of add-in prices
double addInPrices[] = { .89, .25, .59, 1.50, 1.75 };
//bool foundIt = false; // Flag variable
int x, i, j; // Loop control variable
double orderTotal = 2.00; // All orders start with a 2.00 charge
string QUIT = "XXX";
// Get user input
cout << "Enter coffee add-ins followed by XXX to quit: ";
for(i=0; i<NUM_ITEMS; i++) {
cin >> addIn[i];
if(addIn[i] == QUIT) {
i++;
break;
}
}
int foundIt[i];
// Write the rest of the program here.
for(j=0; j<i; j++) {
foundIt[j] = -1;
for(x = 0; x<NUM_ITEMS && foundIt[j] == -1 && addIn[j] != QUIT; x++) {
if (addIn[j] == addIns[x]) {
foundIt[j] = x;
}
}
}
for(j=0; j<i-1; j++) {
cout << addIn[j];
if(foundIt[j] != -1) {
cout << " $" << addInPrices[foundIt[j]] << endl;
orderTotal = orderTotal + addInPrices[foundIt[j]];
}
else {
cout << " - Sorry, we do not carry that." <<endl;
}
}
cout << "$" << orderTotal <<endl;
return 0;
}
Sample Outputs
Enter coffee add-ins followed by XXX to quit: Cream Cinnamon XXX
Cream $0.89
Cinnamon $0.25
$3.14
Enter coffee add-ins followed by XXX to quit: Cream Onion XXX
Cream $0.89
Onion - Sorry, we do not carry that.
$2.89
What I did was made addIn array of srings with NUM_ITEMS size instead of variable. Also, foundIt was made an integer array to keep track of indexes where the items are found in addIns array and -1 if not found.
To only access the items that user has entered in addIn, your QUIT has been made the termination condition in that array.

Answer 3

The structure you are looking for is a while or do/while loop.
To be able to enter "empty" lines use std::getline from.
The structure of your program will then look something like this :
As you can see I have a habit of changing my boolean expressions into functions (predicates). This makes code more readable and predicates reusable in other bits of code.
#include <iostream>
#include <string>
bool is_quit(const std::string& input)
{
return input.length() > 0;
}
bool is_valid_input(const std::string& input)
{
return true; // your own check
}
int main()
{
bool quit = false;
std::string input;
do
{
std::cout << "give input : ";
std::getline(std::cin, input);
quit = is_quit(input);
if (is_valid_input(input) && !quit)
{
std::cout << "ok" << std::endl;
}
} while (!quit);
return 0;
}