rand() function doesn't works properly

Question

I have a problem with rand() function I want to build a program that shows the number of each face of dice when you throw it 6000 times

I wrote this code

#include <iostream>
using namespace std;
#include <iomanip>
using std::setw;
#include <cstdlib>
#include <ctime>
int main()
{
int face ;
int frequency1 =0;
int frequency2 =0;
int frequency3 =0;
int frequency4 =0;
int frequency5 =0;
int frequency6 =0;
for(int counter =1;counter <=6000;counter++){

      face = 1+rand()%6;
      switch(face){
    case 1:
        ++frequency1;
        break;

     case 2:
        ++frequency1;
        break;

     case 3:
        ++frequency1;
        break;

     case 4:
        ++frequency1;
        break;

     case 5:
        ++frequency1;
        break;

     case 6:
        ++frequency1;
        break;
     default:
        cout<<"program should never get here!!! ";
        break;
  }}
  cout<<"the number of face 1 is : "<<frequency1<<endl;
 cout<<"the number of face 2 is : "<<frequency2<<endl;
 cout<<"the number of face 3 is : "<<frequency3<<endl;
 cout<<"the number of face 4 is : "<<frequency4<<endl;
 cout<<"the number of face 5 is : "  <<frequency5<<endl;
 cout<<"the number of face 6 is : "      <<frequency6<<endl;
 return 0;
 }

Every time that i run this code it shows the same thing

the number of face 1 is : 6000
the number of face 2 is : 0
the number of face 3 is : 0
the number of face 4 is : 0
the number of face 5 is : 0
the number of face 6 is : 0

Also, to the flagger, this wasn't necessarily a duplicate. Just a typographical error — Andrew Li, Jun 18 '16 at 08:22
@AndrewL Ah, well you're absolutely right, [Though we should have these powers to close such questions single handed.](http://meta.stackoverflow.com/questions/326250/would-it-be-useful-to-have-an-extension-of-mj%c3%b6lnir-close-voting-powers-for-lang) — πάντα ῥεῖ, Jun 18 '16 at 08:26
@πάνταῥεῖ Completely agree. A question like this should be closed — Andrew Li, Jun 18 '16 at 08:27
You never call `srand()` to seed the generator. Regardless, you shouldn't use `rand()` - use the facilities in `` instead. — Jesper Juhl, Jun 18 '16 at 09:09
Im sorry i'm beginner and i'm following a tutorial that teaching in that way — moein, Jun 18 '16 at 09:20
@Andrew L can you help me ? if i want to write a code like this .how can i do that? Would you do correction this code ?! — moein, Jun 18 '16 at 09:30
@Andrew L as i said am beginner and its difficult to understand something like this — moein, Jun 18 '16 at 15:58
In all the cases you're incrementing frequency1 but not the corresponding case — Andrew Li, Jun 18 '16 at 15:59

score 0 · Accepted Answer · answered Jun 18 '16 at 16:52

You just keep adding to frequency1 instead of other cases. I've tried to explain to you, but you still do not seem to understand. Here is the edited code:

#include <iostream>
using namespace std;
#include <iomanip>
using std::setw;
#include <cstdlib>
#include <ctime>

int main() {
    int face;
    int frequency1 = 0;
    int frequency2 = 0;
    int frequency3 = 0;
    int frequency4 = 0;
    int frequency5 = 0;
    int frequency6 = 0;
    for(int counter =1;counter <=6000;counter++){
        face = 1+rand()%6;
        switch(face){
            case 1:
                ++frequency1;
                break;

            case 2:
                ++frequency2;
                break;

            case 3:
                ++frequency3;
                break;

            case 4:
                ++frequency4;
                break;

            case 5:
                ++frequency5;
                break;

            case 6:
                ++frequency6;
                break;
            default:
                cout<<"program should never get here!!! ";
                break;
        } 
    }
    cout<<"the number of face 1 is : "<<frequency1<<endl;
    cout<<"the number of face 2 is : "<<frequency2<<endl;
    cout<<"the number of face 3 is : "<<frequency3<<endl;
    cout<<"the number of face 4 is : "<<frequency4<<endl;
    cout<<"the number of face 5 is : "<<frequency5<<endl;
    cout<<"the number of face 6 is : "<<frequency6<<endl;
    return 0;
}

As you see, your original code does ++frequency1 (which increments) in all case statements. This edited code should work. I've already explained this.

rand() function doesn't works properly

1 Answers1