Putting output from rand() into an array

Question

I wrote a small dice rolling program that will print out the results of however many dice rolls that are entered. I want to count how much each number occurs so I thought I would put the output from the rand() function into an array and then search the array for the different values. I don't know how to put numbers into an array that are not entered in manually.

    #include <stdio.H>
    #include <stdlib.h>
    #include <time.h>

    int main(void)
    {
        int count; 
        int roll;  

        srand(time(NULL));

       printf("How many dice are being rolled?\n");
       scanf("%d", &count);

       printf("\nDice Rolls\n");
       for (roll = 0; roll < count; roll++)
       {
         printf("%d\n", rand() % 6 + 1);
       }
       return 0;
      }

Oh, goody! A new user. There is no <stdio.H>. I think you meant <stdio.h>. Which book are you reading? — autistic
– autistic, Commented Apr 25, 2013 at 16:02
Yeah, that was a typo. I have the Absolute Beginner's Guide to C, second edition by Greg Perry and C Primer Plus, fifth edition by Stephen Prata. — user2209482
– user2209482, Commented Apr 25, 2013 at 20:32

K Scott Piel · Accepted Answer · 2013-04-25 15:47:10Z

2

    #include <stdio.H>
    #include <stdlib.h>
    #include <time.h>

    int main(void)
    {
        int  count; 
        int  roll;  
        int* history;

        srand(time(NULL));

        printf("How many dice are being rolled?\n");
        scanf("%d", &count);

        history = malloc( sizeof(int) * count );

        if( !history )
        {
            printf( "cannot handle that many dice!\n" );
            exit( -1 );
        }

        printf("\nDice Rolls\n");
        for (roll = 0; roll < count; roll++)
        {
          history[roll] = rand() % 6 + 1;
          printf("%d\n", history[roll]);
        }

        // do something interesting with the history here

        free( history );
        return 0;
      }

answered Apr 25, 2013 at 15:47

K Scott Piel

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2 Comments

Elazar Over a year ago

if you add check for allocation failure, why not add a check for bad scanf too.

K Scott Piel Over a year ago

Because it was not my intent to show him how to use scanf, it was to show him how to correctly allocate and use a dynamic array? ~smile~

Sam I am says Reinstate Monica · Accepted Answer · 2013-04-25 15:47:13Z

0

just put it into the array

for (roll = 0; roll < count; roll++)
{
    myArray[roll] = rand() % 6 + 1;
    printf("%d\n", myArray[roll] );
}

answered Apr 25, 2013 at 15:47

Sam I am says Reinstate Monica

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1 Comment

K Scott Piel Over a year ago

Bear in mind that your solution here does not take into account the fact that the user is inputting a variable number of die to roll, not specifically three die.

Jon H. C · Accepted Answer · 2013-04-25 17:13:06Z

0

If you want to track the number of occurences of each result, you don't even need to save every dice roll.

int result[6] = {} ; // Initialize array of 6 int elements
int current = 0; // holds current random number
for (roll = 0; roll < count
{
     current = rand() % 6;
     result[current]++; // adds one to result[n] of the current random number
     printf("%d\n", current+1);
}

After which you will have an array 0-5 (result), with each element containing the number of each occurence (you will need to add the element number + 1 to get the actual roll). ie. result[0] is the number of occurences of '1'.

edited Apr 25, 2013 at 17:13

answered Apr 25, 2013 at 15:59

Jon H. C

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1 Comment

Jon H. C Over a year ago

Why, thank you. And yes, that is correct twalberg so thanks for that correction as well.

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