[Solved] Program to track the passing of a ball in a circle of 10 people using boolean

Question

I wrote this before the edit, so refer to your original code to see the differences. I added comments to explain what I did.

One of the problems is the lack of {} around the code after the if statements. Without them only the first statement after the if is conditional.

if(newLocation == 0)
      cout << "\nPerson zero has the ball\n"; // Executes based on the condition
      t0 = true; // executes always

Some languages, like Python, use indenting to match things up but C++ does not, so you need braces. I recommend getting into the habit of always using them even when there is only a single line after the conditional. IMO it makes the code easier to read, shows explicit intent, and will never turn into a bug when you add another line that should be conditional but isn’t because you didn’t have the braces.

The other changes are pretty simple. I cleared all of the boolean variables to false before assigning the correct one to true and I used % (mod) to wrap the value around when it is increased past the end.

I don’t use using namespace std; so I added the explicit std:: prefix where needed. I recommend you get in that habit too. It may seem harmless and save you some typing, but someday you’ll regret it, especially if you ever put it in a header.

I’m hoping that your next assignment teaches you how to do this using an array for the variables since it would be so much cleaner and simpler.

#include <iostream>

int main()
{
    bool t0, t1, t2, t3, t4, t5, t6, t7, t8, t9;
    int num1 = 0, num2 = 0;

    // loop forever. The loop will exit when a negative number is entered.
    for(;;)
    {
        // Set all of the variables to false
        t0 = t1 = t2 = t3 = t4 = t5 = t6 = t7 = t8 = t9 = false;

        std::cout << "Enter a number:\n";
        std::cin >> num1;

        // negative number ends the game
        if (num1 < 0)
        {
            std::cout << "Mom says dinner is ready!\n";
            break; // exit loop
        }

        // advance the ball
        // add the new value and use % to wrap it around
        num2 += num1;
        num2 %= 10;

        if (num2 == 0)
        {
            std::cout << "\nPerson zero has the ball\n";
            t0 = true;
        }
        if (num2 == 1)
        {
            std::cout << "\nPerson one has the ball\n";
            t1 = true;
        }
        if (num2 == 2)
        {
            std::cout << "\nPerson two has the ball\n";
            t2 = true;
        }
        if (num2 == 3)
        {
            std::cout << "\nPerson three has the ball\n";
            t3 = true;
        }
        if (num2 == 4)
        {
            std::cout << "\nPerson four has the ball\n";
            t4 = true;
        }
        if (num2 == 5)
        {
            std::cout << "\nPerson five has the ball\n";
            t5 = true;
        }
        if (num2 == 6)
        {
            std::cout << "\nPerson six has the ball\n";
            t6 = true;
        }
        if (num2 == 7)
        {
            std::cout << "\nPerson seven has the ball\n";
            t7 = true;
        }
        if (num2 == 8)
        {
            std::cout << "\nPerson eight has the ball\n";
            t8 = true;
        }
        if (num2 == 9)
        {
            std::cout << "\nPerson nine has the ball\n";
            t9 = true;
        }
    }

    return 0;
}

It’s also possible to replace the if statements with a switch if you wanted to. For something like this it doesn’t really matter, but there are cases where it might be preferred. That would look like this:

switch (num2)
{
case 0:
    std::cout << "\nPerson zero has the ball\n";
    t0 = true;
    break;
case 1:
    std::cout << "\nPerson zero has the ball\n";
    t0 = true;
    break;
}
...

Accepted Answer