generate non repeting random numbers

[eihabisaac]

hey
i wrote this function to generete random numbers. it works but i don't wont these number to be repeated so any idea.
i'm using images to show the numbers.

<script type="text/javascript">

function shuffle()
{
var imgval;
 
document.write("<table border='1'>")
var k=1;
 
for (var i=1;i<=3;i++)
{
    document.write("<tr>");
        for(var j=0;j<3;j++)
        {
        imgval = Math.floor( 1 + Math.random() * 9);
 
        document.write("<td><img src='Image"+(imgval)+".bmp' </td>");
 
        }
        k+=3;
    document.write("</tr>");
}
document.write("</table>");
 
 
}

</script>

[acoder]

Store the numbers in an array and then check against them when generating a new random number.

PS. please use [code] tags when posting code.

[rnd me]

Using Math.round() instead of Math.floor() will help reduce repetition; it splits hairs better.

[eihabisaac]

can u please edit my code to do so. if not i just have this code but i dont know where to put it,, help please

<script type="text/javascript">
<!--

int array = new(9);
 
for (int i=0; i<9; i++)
   array[i] = i+1;
 
shuffle(array);
 
document.writeln("Here are the distinct random numbers:");
 
for (int i=1; i<9; i++)
{
   document.writeln(array[i-1]);
}
 
function shuffle(int array)
{
  int k = 9;
  int RandNum;
  int Temp;
  for (int i=1; i<9; i++)
  {
     RandNum = (int)Math.floor(Math.random()*9);
 
     Temp = array[k-1];
     array[k-1] = array[RandNum];
     array[RandNum] = Temp;
     k--;
  }
}
 

//-->
</script>

[rnd me]

this doesn't look like like javascript to me.

but at any rate, simply replace the word "floor" with the word "round" in your code.

[eihabisaac]

replacing floor with round is not working..any other ideas ,,thnks

[hsriat]

[---- deleted ----]

[hsriat]

@eihabisaac

Try this...

function shuffle()
{
var imgval;
 
//CHANGE 1
var num = "123456789";
 
document.write("<table border='1'>")
var k=1;
 
for (var i=1;i<=3;i++)
{
    document.write("<tr>");
        for(var j=0;j<3;j++)
        {
 
        //CHANGE 2
        imgval = num.charAt(Math.floor(Math.random() * num.length));
        num = num.replace(imgval,'');
 
        document.write("<td><img src='Image"+(imgval)+".bmp' </td>");
 
        }
        k+=3;
    document.write("</tr>");
}
document.write("</table>");
 
 
}

A suggestion: Try to avoid the use of bmp format.

Using Math.round() instead of Math.floor() will help reduce repetition; it splits hairs better.

Well, I have a little disagreement with this.
I think Math.floor() will do it more even than Math.round()

Lets consider this mathematical example by generating randoms between 0 to 9 using each of the above functions.

Using Math.round(), Math.round(Math.random() * 9) will generate randoms between 0 and 9.
And Using Math.floor(), Math.floor(Math.random() * 10) will generate randoms between 0 and 9.

Results (all cases):

random()           round()    floor()
between 0-1         0   1       0
between 1-2         1   2       1
between 2-3         2   3       2
between 3-4         3   4       3
between 4-5         4   5       4
between 5-6         5   6       5
between 6-7         6   7       6
between 7-8         7   8       7
between 8-9         8   9       8
between 9-10         NA         9

So this shows, probability of occurrence of all the integers is equal in case of floor(), but in case of round(), 0 and 9 have half the probability of occurance than other integers.

So, I would recomend to use floor() (or ceil()) rather than round()

Regards,
Harpreet

[acoder]

Just to add, if you want a random number between 1 and 9:

Math.floor(Math.random()* 9) + 1;

eihabisaac, please use [code] tags when posting code (see How to Ask a Question) - the last time you'll be told nicely.

[hsriat]

I think,

Math.floor(Math.random()* 10);

will also do the same.


kind regards

[acoder]

Not quite, that'd give you 0 - 9.

However, your solution (in post #8) for this particular case (1-9) works fine. It'd have to change if you wanted anything greater than 9.

[mrhoo]

I would get the randomized array at one go,
and then build the html string so that
only one write needs to be called.

function shuffleImages(){
    var A= [], i= 1;
    while(i<10) A.push(i++);
    A.sort(function(){return Math.random()-.5})
 
    var str= '<table>\n<tbody>\n';
    var prefix= '<td><img src="Image';
    var suffix= '.bmp"></td>';
    while(A.length){
        str+= '<tr>'+prefix+ 
        A.splice(0,3).join(suffix+prefix)+suffix+'</tr>\n';
    }
    return(str+'</tbody>\n</table>');
    //document.write(str+'</tbody>\n</table>');
}

shuffleImages()

/* returned value:
<table>
<tbody>
<tr><td><img src="Image4.bmp"></td>
<td><img src="Image8.bmp"></td>
<td><img src="Image1.bmp"></td></tr>
<tr><td><img src="Image5.bmp"></td>
<td><img src="Image2.bmp"></td>
<td><img src="Image9.bmp"></td></tr>
<tr><td><img src="Image6.bmp"></td>
<td><img src="Image7.bmp"></td>
<td><img src="Image3.bmp"></td></tr>
</tbody>
</table>
*/