generating random numbers

- make an int array of 25
- fill all with numbers from 1 to 25 (ordered)
- repeat 100 times this:
     select two random numbers from 1 to 25
     interchange both array elements at the random indexes generated
- now you have a list of 25 items un-ordered, use this numbers to generate button labels

#include <cstdlib>

int getRandomInt(int min, int max)
{
    int range = (max – min);
    return ( (range*rand()) / (RAND_MAX+1)) + min;
}

Or you can do it this. Less code but slower when running:

int getRandomInt(int min, int max)
{
    int range = (max – min);
    return ( rand()%range ) + min;
}

Should probably inline those too since they are short.

The getRandomInt answer won't work because there is nothing to prevent duplicates. Each button needs to contain a distinct number, but there is nothing to stop getRandomInt returning eg 21 twice in 25 calls.

That's why I created an ordered list, random algorithm is used to dis-order the array, not to obtain numbers between 1-25

int label[25];
int a, b, temp;

for (int cont=0; cont<25; cont++)
     label[cont] = cont+1;

for (cont=0; cont<100; cont++)  // I think 100 times will be statistical enough
{
      a = rand()%25;
      b = rand()%25;
      t = label[a];
      label[a] = label[b];
      label[b] = t;
}

// now array is disordered

So now I put 't' instead of 'ok' in CreateWindow?

for (x=0; x<5; x++)
            for (y=0; y<5; y++) {
            hwndButton = CreateWindow ("BUTTON", t,
            WS_CHILD | WS_VISIBLE,
            20+x*37, 20+y*37, 35, 35,
            hwnd,
            (HMENU)"", NULL, NULL);
            }
            break;

what should i write instead of ""?

The above code compiles and runs ok. My only problem is that everytime i run it, the numbered buttons always appear in the same order i.e. 13, 8, 24...
I would like the numbers to change positions every time i run it.

put this line after char txtlabel[3]:

srand( (unsigned)time( NULL ) );

Thanks.  but i have another small problem.
what if i want an 8 by 8 grid?

int labelb[64];

for (int cont=0; cont<64; cont++)
     labelb[coant] = cont+1;

for (cont=0; cont<100; cont++)  
{
      a = rand()%64;
      b = rand()%64;
      t = label[a];
      labelb[a] = labelb[b];
      labelb[b] = t;
}

char txtlabelb[3];

for (x=0; x<8; x++)
    for (y=0; y<8; y++) {
            sprintf(txtlabelb, "%i", label[x*5+y]);
            hwndButton = CreateWindow ("BUTTON", txtlabelb,
            WS_CHILD | WS_VISIBLE,
            20+x*37, 20+y*37, 35, 35,
            hwnd,
            (HMENU)"", NULL, NULL);
}

It runs ok but does not give numbers from 1 to 64. It generates strange numbers.

Pay attention to this:

     labelb[cont] = cont+1; // I guess it is a typing error

     sprintf(txtlabelb, "%i", label[x*8+y]);    // Multiply by 8 this time

I changed the mistakes but it is still giving me strange numbers like 273, 4242 and other large numbers that do not "fit" in the button.

     t = label[a];

must be

      t = labelb[a];

BTW. I made a mistake:
srand( (unsigned)time( NULL ) );
must be after
int labelb[64]; (or int label[25])

I also found another mistake :

sprintf(txtlabelb, "%i", label[x*8+y]);

I forgot to change label to label b.

Thanks. Now everything works ok.

Now I will take a rest