Saving each iteration of an accumulator? - c++

Question

(Yes this WAS homework, but already completed, I'm just trying to improve it now for practice)
This is basically a sales calculator, that allows you to have multiple inputs for sales items, then displays the total, sales tax, and grand total.
The modification I'm trying to make, is that I want to be able to SAVE the cost of each number of items in a variable, without them overlapping memory, and then be able to call them above the grand total, so you can see what each item was worth.
===========================================================================
//importing libraries for cin and cout, as well as setw() and setprecision()
#include <iostream>
#include <iomanip>
using namespace std; //sets all code to standard syntax
int main(){ //initializes the main function
//initializing variables
char answer = ' ';
int saleItems = 0;
double saleTax = 0.0;
double grandTotal = 0.0;
double itemValue = 0.0;
double titemValue = 0.0;
double taxPerc = 0.0;
//begins a post-test loop
do {
titemValue = 0.0; //makes sure the accumulator resets WITHIN the loop
//prompts for sale items amount
cout << "How many sales items do you have? : ";
cin >> saleItems;
//creates a loop that displays the prompt for each iteration of saleItems
for (int x = 1; x <= saleItems; x += 1){
cout << "Enter in the value of sales item " << x << " : $";
cin >> itemValue;
titemValue += itemValue; //accumulator for adding up the iterated values
}
//prompts the user to enter a sales percentage
cout << endl << endl;
cout << "Enter in the sales tax percentage(Enter 10 for 10%): ";
cin >> taxPerc;
cout << endl << endl;
//processes the variables after taxPerc has been given
saleTax = titemValue * (taxPerc / 100);
grandTotal = titemValue + saleTax;
//sets decimal precision to 2 places
cout << fixed << setprecision(2);
//displays receipt with the calculated and input values
cout << "********************************************" << endl;
cout << "******** S A L E S R E C E I P T ********" << endl;
cout << "********************************************" << endl;
cout << "** **" << endl;
cout << "** **" << endl;
cout << "** **" << endl;
cout << "** **" << endl;
cout << "** Total Sales $" << setw(9) << titemValue << " **" << endl;
cout << "** Sales Tax $" << setw(9) << saleTax << " **" << endl;
cout << "** ---------- **" << endl;
cout << "** Grand Total $" << setw(9) << grandTotal << " **" << endl;
cout << "** **" << endl;
cout << "** **" << endl;
cout << "********************************************" << endl << endl << endl;
//prompts user to begin loop again
cout << "Do you want to run this program again? (Y/N):";
cin >> answer;
answer = toupper(answer);
cout << endl << endl;
} while (answer == 'Y');
===========================================================================
So, essentially, I need to be able to save each itemValue to multiple different values without the loop repeating itself, and just replacing them, and I can't really see how I can do that considering the accumulator will just keep looping, and adding up the itemValue values.

Answer 1

Here is one way to use an simple array to store the item values.
Declare an array at the top. Note: you will have to give it a fixed size. There are ways to have a variable size, but they get more complex (such as vectors). It is better to specify the size using a constant, rather than a hard coded number, as you will need the constant later.
const int maxSaleItems = 100;
double itemValues[maxSaleItems];
After you have asked the user for the number of items, max sure they haven't entered a number that is too big.
cout << "How many sales items do you have? : ";
cin >> saleItems;
if (saleItems > maxSaleItems) {
cout << "Sorry, I can only handle " << maxSaleItems << " items.";
continue;
}
Inside the loop where you are inputting the item values, save the item value to the array:
cout << "Enter in the value of sales item " << x << " : $";
cin >> itemValue;
titemValue += itemValue; //accumulator for adding up the iterated values
itemValues[x - 1] = itemValue;
Note the x-1 in the array access - arrays are 0 based (i.e. their index starts from 0). Normally I would loop x from 0 to < saleItems, but I didn't want to change your existing loop.
When printing the receipt, add a loop which prints out all the values (you will need to add formatting):
cout << "** **" << endl;
for (int x = 1; x <= saleItems; x += 1){
cout << "** Item " << x << " $" << itemValues[x-1] << " **" <<endl;
}
cout << "** **" << endl;
As I said in the comments, using std::vector would be better, but if you aren't up to that yet, arrays will do.
Edit: Simple vector example.
To add vectors you need to include the appropriate header:
#include <vector>
No need for maxSaleItems any more, as vectors can grow. Declare the vector variable. The <double> makes it a vector that contains double values:
std::vector<double> itemValues;
Inside the loop, instead of setting the array value for the new item by location, just add it to the end of the vector using push_back.
cout << "Enter in the value of sales item " << x << " : $";
cin >> itemValue;
titemValue += itemValue; //accumulator for adding up the iterated values
itemValues.push_back(itemValue);
The printing receipt code, can be left exactly as it was for the array version, as you can access vectors like arrays:
cout << "** **" << endl;
for (int x = 1; x <= saleItems; x += 1){
cout << "** Item " << x << " $" << itemValues[x-1] << " **" <<endl;
}
cout << "** **" << endl;
There are other changes you could do to make the vector version simpler, but I wanted to change as little as possible.