"hour" counter won't reset, after the program is run again - c++

Question

I can't figure out how to reset the "hour" counter.
The program runs perfect on the 1st run, but when user enters another set of hours, hours start numbering between 110-117.
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
const float initialVolume = 130.00;
const float decreaseRate = 0.13;
int counter = 0;
int main()
{
int hours,i,j,k;
float remainingVolume, halfVolume, zeroVolume;
while (cout << "Enter hours to see how much caffeine "
<< "is left in your body, after you drank your coffee: " && cin >> hours)
{
cout << endl;
cout << fixed << showpoint << setprecision(4);
remainingVolume = initialVolume;
for (i = 0; i < hours; i++)
{
counter++;
remainingVolume = remainingVolume - decreaseRate * remainingVolume;
cout << "Hour " << setw(5) << counter << setw(15) << remainingVolume << "mg"<< endl;
}
for (j = 0, halfVolume = 130.00; halfVolume > 65.0000; j++)
{
counter++;
halfVolume = halfVolume - decreaseRate * halfVolume;
}
for (k = 0, zeroVolume = 130.00; zeroVolume > 0.0001; k++)
{
counter++;
zeroVolume = zeroVolume - decreaseRate * zeroVolume;
}
cout << "\n" << endl;
cout << "It will take " << j << " hours to get caffeine levels to 65mg. \n" << endl;
cout << "It will take " << k << " hours to get caffeine levels to 0mg. \n\n" << endl;
}
return 0;
}
output:
Enter hours to see how much caffeine is left in your body, after you
drank your coffee: 4
Hour 1 113.1000mg
Hour 2 98.3970mg
Hour 3 85.6054mg
Hour 4 74.4767mg
Enter hours to see how much caffeine is left in your body, after you
drank your coffee: 3
Hour 112 113.1000mg
Hour 113 98.3970mg
Hour 114 85.6054mg

Answer 1

You are never resetting your counter value. You initialise it to 0 and then increase it in every loop. you need to reset it to 0 every time they enter a new number (ie in your while loop).
The best solution would be to have to counter variable as a local variable declared in the loop:
while (cout << "Enter hours to see how much caffeine "
<< "is left in your body, after you drank your coffee: " && cin >> hours)
{
int counter=0;
cout << endl;
cout << fixed << showpoint << setprecision(4);
remainingVolume = initialVolume;
for (i = 0; i < hours; i++)
{
counter++;
remainingVolume = remainingVolume - decreaseRate * remainingVolume;
cout << "Hour " << setw(5) << counter << setw(15) << remainingVolume << "mg"<< endl;
}
for (j = 0, halfVolume = 130.00; halfVolume > 65.0000; j++)
{
counter++;
halfVolume = halfVolume - decreaseRate * halfVolume;
}
for (k = 0, zeroVolume = 130.00; zeroVolume > 0.0001; k++)
{
counter++;
zeroVolume = zeroVolume - decreaseRate * zeroVolume;
}
cout << "\n" << endl;
cout << "It will take " << j << " hours to get caffeine levels to 65mg. \n" << endl;
cout << "It will take " << k << " hours to get caffeine levels to 0mg. \n\n" << endl;
}
return 0;
}

Answer 2

You need to reset the counter after you're done with your iteration:
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
const float initialVolume = 130.00;
const float decreaseRate = 0.13;
int counter = 0;
int main()
{
int hours,i,j,k;
float remainingVolume, halfVolume, zeroVolume;
while (cout << "Enter hours to see how much caffeine "
<< "is left in your body, after you drank your coffee: " && cin >> hours)
{
cout << endl;
cout << fixed << showpoint << setprecision(4);
remainingVolume = initialVolume;
for (i = 0; i < hours; i++)
{
counter++;
remainingVolume = remainingVolume - decreaseRate * remainingVolume;
cout << "Hour " << setw(5) << counter << setw(15) << remainingVolume << "mg"<< endl;
}
for (j = 0, halfVolume = 130.00; halfVolume > 65.0000; j++)
{
counter++;
halfVolume = halfVolume - decreaseRate * halfVolume;
}
for (k = 0, zeroVolume = 130.00; zeroVolume > 0.0001; k++)
{
counter++;
zeroVolume = zeroVolume - decreaseRate * zeroVolume;
}
cout << "\n" << endl;
cout << "It will take " << j << " hours to get caffeine levels to 65mg. \n" << endl;
cout << "It will take " << k << " hours to get caffeine levels to 0mg. \n\n" << endl;
counter = 0; // <--
}
return 0;
}