Thread: Dice Rolling Problem

Code:

  num[ total - 1 ] = 1;

You never change the elements of num[] anywhere else. The value of num[0] is an uninitialized value, since you don't initialize the elements of num[] to zero and total is never 1. Also, roll_die() should be declared as

Code:

int roll_die()

and the variable roll should be a local variable in the function body, since you never use the value you're presently passing.

Edit: Just to be clear, what you need to do is INCREMENT num[total-1], not set it to 1:

Code:

  ++num[total-1];

but don't forget to initialize all the elements of num[] to 0 first.

Edit: It should also be

Code:

  int num[12];

Edit: The guaranteed maximum value of a signed short or int is only 32767, but num[] should be a type with a guaranteed maximum of at least 36000. An unsigned short or int has a guaranteed maximum of 65535. Of course, it's very unlikely (read "lifetime-of-the-universe unlikely") that you would get a single value more than 32767 times with 36000 rolls, but still.

Code:

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int roll_die();
void display( int [] );

//This is kind of stupid, but whatever
const int MAX_SUM = 6 + 6;
const int NUM_ROLLS = 36000;


int main()
{
    int num[MAX_SUM];

    srand( time( 0 ) );

    for (int i = 0; i < MAX_SUM; i++)
	    num[i] = 0;

    for ( int a = 0; a < 36000; a++ ) 
	    num[roll_die() + roll_die() - 1]++;
    
    display( num );
 
}



int roll_die( )
{
    int roll = (rand() &#37; 6) + 1;
    return roll;
}


void display( int number [] )
{
    //Notice I changed b's initial value to 1 
    for ( int b = 1; b < 12; b++ )
        cout << b + 1 << " was rolled " << number[ b ] << " times.\n";
}