# Playing with a Full Deck

Excel is great at generating random numbers, but it is less great at filling a range of cells with random numbers in which no particular number is repeated twice. For instance, you might want to populate 52 cells with the numbers 1 through 52, in random order. (This is very similar to choosing cards from a deck in random order, where a particular card can only be chosen once. Thus the title for this tip.)

There obviously is no built-in Excel function to provide this capability, so you are left to work with macros. Fortunately, such a macro is not terribly difficult to create. The following macro will do the trick nicely:

```Sub FillRand()
Dim nums() As Integer
Dim maxval As Integer
Dim nrows As Integer, ncols As Integer
Dim j As Integer, k As Integer
Dim Ptr As Integer
Randomize

Set s = Selection
maxval = s.Cells.Count
nrows = s.Rows.Count
ncols = s.Columns.Count

ReDim nums(maxval, 2)

'Fill the initial array
For j = 1 To maxval
nums(j, 1) = j
nums(j, 2) = Int((Rnd * maxval) + 1)
Next j

'Sort the array based on the random numbers
For j = 1 To maxval - 1
Ptr = j
For k = j + 1 To maxval
If nums(Ptr, 2) > nums(k, 2) Then Ptr = k
Next k
If Ptr  j Then
k = nums(Ptr, 1)
nums(Ptr, 1) = nums(j, 1)
nums(j, 1) = k
k = nums(Ptr, 2)
nums(Ptr, 2) = nums(j, 2)
nums(j, 2) = k
End If
Next j

'Fill in the cells
Ptr = 0
For j = 1 To nrows
For k = 1 To ncols
Ptr = Ptr + 1
s.Cells(j, k) = nums(Ptr, 1)
Next k
Next j
End Sub
```

This macro uses a two-dimensional array (nums) to figure out which numbers to use and the order in which they should be used. Near the beginning of the macro the array is filled with a static number (1 through the number of cells) and a random number between 1 and the number of cells. This second number is then used to sort the array. Once the array is stored, it is a simple matter to place the original numbers in the cells.

By the way, the reason a two-dimensional array is used is because the Rnd function that VBA uses to generate random numbers can return duplicate values. Thus, even through the second dimension of the array can have duplicates in it, when the array is finally sorted, the first dimension will not have duplicates.

To use the macro, start by selecting the cells you want to have filled with sequential values in a random order. When you run the macro, that range is filled. For instance, if you select ten cells and then run the macro, then those cells are filled with the numbers 1 through 10, in random order.