C++ math calculation for determining change using char icons - c++

Question

cout << "Your change is " << change << ". Here's your change:";
char q = '#';
double ccounter = 0;
while(ccounter <= (change - .24)){
cout << q;
ccounter = ccounter + .25;
}
char d = '^';
while(ccounter <= (change - .09))
{
cout << d;
ccounter = ccounter + .10;
}
char n = '&';
while(ccounter <= (change - .04)){
cout << n;
ccounter = ccounter + .05;
}
char p = '*';
while(ccounter <= change){
cout << p;
ccounter = ccounter + .01;
}
return 0;
}
Once your customer pays you the amount that is greater or equal to 1.87, give them the change using the symbols listed above. So, for example, if your customer paid with 5 dollars, you should print out:
Your change is 3.13. Here’s your change: $$$^***
First is the code second block is the prompt.
When the user inputs 3 for what they'd like to pay everything is fine, but 4 gets four penny icons when really it should be three since the change is 0.13.
Any help or advice would be greatly appreciated!
thank you guys:)
[ * ] = Penny (1 cent)
[ & ] = Nickel (5 cents)
[ ^ ] = Dime (10 cents)
[ # ] = Quarter (25 cents)
[ $ ] = 1 dollar

Answer 1

The loop is ending at the wrong time because the ccounter variable is accumulating errors from floating point round-off. If you calculate 2 + 0.1 + 0.01 + 0.01 + 0.01, you get 2.1299999999999994. You should change everything to use integer math, i.e. start with a counter of 213 cents, then subtract 25, 10, 5, and 1 from that. If you stick with integer math, it'll work reliably.

Answer 2

Your loop termination conditions appear to all have one-off errors. It may be more clear to write the code as:
cout << "Your change is " << change << ". Here's your change:";
char q = '#';
double ccounter = 0;
while((change - ccounter) >= 0.25)
{
cout << q;
ccounter = ccounter + .25;
}
char d = '^';
while((change - ccounter) >= 0.10)
{
cout << d;
ccounter = ccounter + .10;
}
char n = '&';
while((change - ccounter) >= 0.05)
{
cout << n;
ccounter = ccounter + .05;
}
char p = '*';
while((change - ccounter) >= 0.01 )
{
cout << p;
ccounter = ccounter + .01;
}
return 0;
}