Trouble calculating percentage in C++ dice program

[d0ugg]

I'm writing a program that will have to roll the dice A and dice B one million times, and calculate the percentage of times that the dies will be equal.

I'm having trouble to figure out how the percentage will work.

Here is my code:

 
#include <ctime>
#include <iostream>
using namespace std;
 
const double roll = 1000000;
 
int rolldie() //statement will give u 6
{
return (rand()%6+1);
}
 
void Randomize() 
{
srand( (unsigned)time( NULL ) ) ;
}
 
int main()
{
    int diceA;
    int diceB;
    int totals;
    int i;
    cout << "Rolling dices one million times\n";
    Randomize();
 
    for(i=0;i<roll;i++)
    {    
        diceA = rolldie();
        diceB = rolldie();
        int    totals = diceA + diceB;
        totals++;
    }
 
    if(diceA==diceB)
    {
        cout << "Doubles occurred" << totals / 1000000 << "percent of the time.";
    }
 
    return 0;
}
 

Thanks in advance,

Doug

[JosAH]

So,
I did what you told me

for(i=0;i<roll;i++)
    {    
        diceA = rolldie();
        diceB = rolldie();
        totals += diceA + diceB;
    }
 

But not it seems that is running, but it's not printing anything.
And I also put the int totals out of the loop..

Any ideas why is not printing the percentage?

Thank you so much for the help,

Doug

Did you read my reply? You should check whether or not diceA and diceB are
equal; if so you should increment a counter. The way you do it now you simply
add both scores to the running total; that is wrong.

kind regards,

Jos

[kreagan]

So,
I did what you told me

for(i=0;i<roll;i++)
    {    
        diceA = rolldie();
        diceB = rolldie();
        totals += diceA + diceB;
    }
 

But not it seems that is running, but it's not printing anything.
And I also put the int totals out of the loop..

Any ideas why is not printing the percentage?

Thank you so much for the help,

Doug

Did you read anyone's posts except sicarie? If you did, you should have known that his suggestion was solving another problem. Also, your if statement is in the wrong place. You will only print out if diceA and diceB are equal on the last iteration.

[d0ugg]

Hello,

Sorry for been very stupid.

Well, I tried to include it on the loop but still doesn't work. It compiles but when I run, it really doesn't show the right answer.
Here is my "fixed" code.

#include <ctime>
#include <iostream>
using namespace std;
 
const double roll = 1000000;
int totals;
 
int rolldie() //statement will give u 6
{
return (rand()%6+1);
}
 
void Randomize() 
{
srand( (unsigned)time( NULL ) ) ;
}
 
int main()
{
    int diceA;
    int diceB;
    int i;
    cout << "Rolling dices one million times\n";
    Randomize();
 
    for(i=0;i<roll;i++)
    {    
        diceA = rolldie();
        diceB = rolldie();
 
        for(diceA=diceB;totals++;)
        {
            cout << "Doubles occurred" << totals / 1000000 << "percent of the time.";
        }
    }
 
    return 0;
}
 

Thank you for the help,

DOug

[sicarie]

    for(i=0;i<roll;i++)
    {    
        diceA = rolldie();
        diceB = rolldie();
 
        for(diceA=diceB;totals++;)
        {
            cout << "Doubles occurred" << totals / 1000000 << "percent of the time.";
        }
    }
 

Okay, why did you decide to put the 'for(diceA=dice B;totals++;) in the for loop?

That's the thing you want to happen one time, and if it is in the for loop, it will happen every time. It would seem to me you want that outside the for loop. (Though you still want to have _something_ in there to increment totals if a is equal to b.)

Also, the diceA=diceB means you are going to assign the value of B to A. You want the '==' double equals, which is the conditional. If diceA==diceB, then do whatever - you don't need a for loop, in fact, I don't think you need anything there, just the print statement.

[JosAH]

Sorry for been very stupid.

Nobody thinks your stupid; you just don't 'speak' C or C++ yet so lets forget
about that for a second. I give you a piece of paper and a pencil. I'm going
to roll two dice 'n' times. After every roll I show your their score.

What do you have to do after I rolled those dice? Be quick because I'm going
to roll them again. Just use simple English please.

kind regards,

Jos

[d0ugg]

Oh okay,
But my now my question is..
I don't know how to add in the for loop if (diceA == diceB = totals) and than increment.. Is there anywhere that I can look for that?

[d0ugg]

Oh and by the way,

After I roll the dices I need to calculate the percentage of times that the dices will have the same value, when the dices will equal to 7 and also when the dices will each have values of 1.

[Ganon11]

As Jos suggested, think about how you might tackle this problem without a computer. A fundamental idea about programming is an algorithm - a series of steps you must take in order to solve the problem. You can think of a correct algorithm without touching a computer. Once you have this algorithm, it is easy to translate this into code.

Suppose I want to write a program to calculate the average score on some test I give. I have all the student's results; now what do I do? Well, I would add up all the student's results and divide by the number of students, giving me the average score per student. My algorithm would be:

1) Retrieve the scores from my students
2) Total these scores
3) Divide this total by the total number of students

From this algorithm, it would be simple to write a program.

What you need to do is to spend some time away from your program. Stop thinking in code for a bit, and instead focus on an algorithm to determine the percentage of doubles. Once you have figured out how to do this without a computer, then and only then focus on writing code for that algorithm.

(By the way, as Jos said, no one thinks you're stupid. There's a huge difference between 'stupid' and 'inexperienced with programming. I can almost guarantee you that most, if not all, of the moderators and experts here were, at one point, as confused as you. What tells me that you are, in fact, not stupid, is that you have so far refused to stop trying to solve this problem, and that you were smart enough to ask for help when you needed it. So, from one rookie to another (because I don't have much experience either ;) ), don't feel bad when you ask for help.)

[JosAH]

Oh and by the way,

After I roll the dices I need to calculate the percentage of times that the dices will have the same value, when the dices will equal to 7 and also when the dices will each have values of 1.

You're way too fast for me; lets go slowly: I present you an arbitrary pair of dice;
what do you do? hint: you do have a counter which you can increment. What
do you do if I present you the pair 5,4? Do you increment that counter if you
want that counter to represent the number of equal pairs I've shown you?
I guess not. You do increment that counter when I present you a pair, say: 3, 3.

So basically this is what's happening:

me: I show you a pair x, y
   you: you do something that makes sense.
 

Your turn: what makes sense here? Note that I sneakily indented that 'pseudo'
code because I'm gonna show you a lot of pair of dice and you have to make
a sensible decision over and over again.

kind regards,

Jos

[kreagan]

Glad to see you are still trying this problem. Like many people already said, we all had to start at the beginning. Along with the suggestions on writing psuedo code without thinking about code (which is a good practice even for experienced programmers), place couts everywhere expecially for loops and if statements. If you have a debugger, use that too.

For example, I added new couts to your original post.

    for(i=0;i<roll;i++)
    {    
                cout << "Entering For Loop. i =" << i;  //added
        diceA = rolldie();
                cout << "DiceA is" << diceA;   //added debug line
        diceB = rolldie();
                cout <<"DiceB is" << diceB;   //added debug line
        int totals = diceA + diceB;
                cout <<"totals is when dice are added together" << totals;
        totals++;
                cout <<"totals is after increment" << totals;
    }

This can allow you to see the flow of your code. Also, it will point out parts that you expected to behaive differently. When I started, I used them heavily and could see the logic flow of the program before I was confortable with reading code.

Good luck