Problem with random number generator

[metalguy]

This code keeps giving me the same random number, can somone please tell me why?


{
int RandomNumber;
int i;
int j;

for (i = 0; i < SCREEN_HEIGHT; i++) /*For the number of rows on the console*/
{
for (j = 0; j < SCREEN_WIDTH; j++)/*For the number of columns on the console*/
{

//Sleep();

srand(time(NULL));

RandomNumber = 1 + (int) (3.0 * rand() / (RAND_MAX + 1.0));
switch (RandomNumber)
{
case 1 : write_char('1');
break;
case 2 : write_char('0');
break;
case 3 : write_char(' ');
break;
}/*switch (random_number)*/
}
}
}

[Wynd]

Not sure...this code works fine for me. One thing that could make it screw up though is you only need to do srand() once.

#include <iostream>
#include <ctime>
using namespace std;

const SCREEN_HEIGHT = 25;
const SCREEN_WIDTH = 80;

int main()
{
    srand(time(NULL));

    int RandomNumber;
    int i;
    int j;

    for (i = 0; i < SCREEN_HEIGHT; i++)
    {
        for (j = 0; j < SCREEN_WIDTH; j++)
        {
            RandomNumber = 1 + (int)(3.0 * rand() / (RAND_MAX + 1.0));

            switch (RandomNumber)
            {
            case 1:
                cout << 1;
                break;
            case 2:
                cout << 0;
                break;
            case 3:
                cout << ' ';
                break;
            }
        }
    }
    return 0;
}

[ii3ejoe]

how would you change the above code to include numbers an letters. like say you entered : 1m4j3js52 : and wanted that randomized?

[jim mcnamara]

I don't see a duplicate srand() call, unless you edited your post
Your code and Wynd's code both work.

The real isssue is the fact that you are choosing only three random values. It's not far out of consideration to think that you could have three calls returning the same value.

I know when I wrote my first random number generator a long time ago, we were testing it and thought it had a problem for the same reason you see. It kept repeating the same value. But we were only choosing 4 values.

[riis]

Wynd meant that, because the srand was inside the for-loops, the randomizer always initializes with the same seed. The loop is executed within one second, so the time, used as a seed, didn't change.