Who doesn't like discounts? Exercise C++ [SPOILER]

Question

Hey all,
Been blocked on this exercise for a while now. Here's the subject:
A supermarket has launched a campaign offering a 15% discount on 3 items.
Write a program that takes the total price for every purchase as input and outputs the relevant discount.

## code ##
#include <iostream>
using namespace std;

int main()
{
int purchaseAmount = 0;
int totalPrice;

//your code goes here
do {
cin >> totalPrice;
float purchaseAmount = totalPrice * 0.15;
cout << purchaseAmount << endl;
} while (totalPrice); // Tried (totalPrice < 3)

return 0;
}
The result is an infinite loop with the last input. I know there's a detail I've miss but still can't figure out what T_T

Any tips? :/

Answer 1

Right now, you continue iterating while "totalPrice" is unequal to zero. However, if there is no more input, std::cin will not write anything into it, meaning it will keep its value from the third iteration and result in an infinite loop.
To fix this, you could introduce a counter variable:

int iterations = 3;
...
do {
...
} while ( --iterations );

Or check if the input stream is still usable:

do {
...
} while ( cin.good() );

But, to be honest, if there are always a fixed number of inputs, a for loop would probably be a better suit than a do-while loop, this task is kind of a bad example for it.

Answer 2

@Shadow, tried the (while(cin.good()); well, the problem is that I haven't learn that part x)
Tried to the 1st and it work perfectly. I might have found my problem, is that I was focusing on the code bellow // your code goes here.
Thx mate! :)