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I am making this code for a random dice roller and I want to get a random number until I get three 6's on the dice. For some reason this produces the same number for all runs, but on my for loop it works. Can I get some help getting this to work?

The pesky While loop in question:

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

int Ran(int max) {
return (rand() % max)+ 1;
}

int main(){

    int max = 6;
    int nsuc = 0, ncount = 0;
    int matt = 40;
    srand((unsigned) time(0));

    for(int i = 1; i <= 20; i++){
        while(!(nsuc >= 3)){
            int nr = Ran(max);
            if(nr < matt){
                ncount++;
                if(nr == 6){
                    nsuc++;
                }
            }
        }
        printf("Number of rolls until 3 6's = %d\n", ncount);
    }
}

Cleaned up the for loop so it's easier to read now:

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


void Shuffle() {
srand((unsigned) time(NULL));
}

int Ran(int max) {
return (rand() % max)+ 1;
}

void binomial(int run, int max, int btrials, int *array, int scount){

    for(int j = 1; j<=run; j++){
        for (int i=1;i<=btrials;i++){
            int r = Ran(max);
            if(r == 6){
            scount++;
            }
        printf("Trial %i, roll = %d\n",i , r);
        }
        array[j-1] = scount;
        scount = 0;
        printf("\nEnd of Run %d\n\n",j);
    }

}

int main(){

    int Runs;
    printf("How many runs do you want to do? > ");
    scanf("%d", &Runs);
    printf("\n");

    int bdist[20];
    int distcount = 0;
    int max = 6;
    int btrials = 20;
    int suc[Runs+1];
    int scount = 0;



    Shuffle();
    binomial(Runs, max, btrials, suc, scount);

    printf("All counts of succesful 6 rolls.\n");

    /*
    for(int z = 1; z<=Runs; z++){
        printf("Run %d has %d 6's\n", z, suc[z-1]);
    }
    */

    for(int k = 0; k<=btrials; k++){
        for(int j = 1; j<=Runs; j++){
            if(suc[j-1] == k){
                distcount++;
            }     
        }
        bdist[k] = distcount;
        distcount = 0;
    }

    for(int t = 0; t<=btrials; t++){
        printf("Number of runs with %d 6s = %d\n", t, bdist[t]);
    }

    return 0;

}
Jongware
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Travis Myers
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2 Answers2

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You never reset nsuc or ncount in the first version with the while loop. After the first time thru, they still have their values from the previous loop so you get the same output.

1201ProgramAlarm
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  • Yea you got it, I was so focused on it being rand() I just forgot to do something so basic. Thanks for the help, I supposed I should take a break from coding for today. – Travis Myers Mar 07 '20 at 02:14
0

Not an answer strictly related to the question, but something I noticed.

If I recall, generating ranged random numbers using the (rand % max)+ 1 idiom is not advised.

One.

Two

Jordan
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  • This does not answer the question, as you said. It would make a fair comment. Please wait until you have a few more points – be warned, posting comments as answers will *not help* you getting there. – Jongware Mar 08 '20 at 01:05
  • Will do, just wanted to do my part. – Jordan Mar 08 '20 at 01:06