Dice program..need help

[mehly2020]

I need help on getting started with a dice program that will output as many random numbers from 1 to 6 and as many rolls as the user requests....And then how many times each number shows up from the number of rolls...

[Banfa]

Create a function that produces a number from 1 to 6.

Then implement this pseudo code

GET number of require dice rolls
 
FOR each required dice roll
    Get Dice Roll
 
    Increment Count of number rolled
END FOR
 
PRINT Dice roll statistics
 

You can easily store the count of each number rolled in an array of 6 integers.

[apusateri]

I need help on getting started with a dice program that will output as many random numbers from 1 to 6 and as many rolls as the user requests....And then how many times each number shows up from the number of rolls...

Try this out, threw it together real quick here because I've got to get back to work, but I compiled it and it should run.

You can clean up the code and rename variables, etc... for your own purposes:

#include <iostream>
#include <cstdlib>
#include <time.h>
 
using namespace std;
 
int rollDice();
 
int main(int argc, char* argv)
{
    int numRolls;
    int arrRolls[6];
    int dieRoll;
 
    srand((unsigned)time(0));
 
    cout << "How many times would you like to roll the dice?" << endl;
    cin >> numRolls;
 
    for (int k = 0; k < 6; k++)
    {
        arrRolls[k] = 0;
    }
 
    for (int i = 1; i <= numRolls; i++)
    {
        dieRoll = rollDice();
        cout << "Die Roll " << i << ": " << dieRoll << endl;
        arrRolls[dieRoll - 1]++;
    }
 
    for (int j = 0; j < 6; j++)
    {
        cout << "The number " << j + 1 << " was rolled " << arrRolls[j] << " times." << endl;
    }
}
 
int rollDice()
{
    int result;
 
    result = (rand() % 6) + 1;
 
    return result;
}
 

[Banfa]

result = (rand() % 6) + 1;

This is not a good way to get a random value between 1 and 6 because the normal algorithm implemented by rand() does not give very good randomness in the low order bits of the value produced.

[apusateri]

This is not a good way to get a random value between 1 and 6 because the normal algorithm implemented by rand() does not give very good randomness in the low order bits of the value produced.

What's a better way?

With 1000 iterations this one seems fairly random, to me:

1 - 168
2 - 150
3 - 170
4 - 173
5 - 168
6 - 171

[Banfa]

This is a better way

(int)((double)rand() / ((double)RAND_MAX + 1) * N)

Get values in the range 0 - (N-1)

If you want 1-6 then N=6 and add 1 to the result.

If you don't want to use floating point arrithmatic you can use

rand() / (RAND_MAX / N + 1)

However if N is very close to RAND_MAX both these methods break down and you require something else.

It's all explained here.

[apusateri]

This is a better way

(int)((double)rand() / ((double)RAND_MAX + 1) * N)

Get values in the range 0 - (N-1)

If you want 1-6 then N=6 and add 1 to the result.

If you don't want to use floating point arrithmatic you can use

rand() / (RAND_MAX / N + 1)

However if N is very close to RAND_MAX both these methods break down and you require something else.

It's all explained here.

Thanks for the reference, Banfa - hadn't looked at that link before, just going off of the knowledge that I already have. This makes sense, though - appreciate the feedback.