Shuffle numbers

[Brian's Man Cave]

Is there a way to shuffle a group of numbers randomly. I remember in a different programming language I was able to create an array of say 5 numbers. Then grab at random each number to create a new array of the same 5 numbers but in a different order. Or is there an easier method? 

[Arnauld]

A popular and efficient shuffle algorithm is Fisher-Yates. It runs in linear time. (I'm using it for instance in Defender of the Crown to shuffle the lords at the beginning of the game.)

 

Quoting the pseudo-code from Wikipedia:

 

-- To shuffle an array a of n elements (indices 0..n-1):
for i from n−1 downto 1 do
     j ← random integer such that 0 ≤ j ≤ i
     exchange a[j] and a[i]

 

[+nanochess]

The easiest method would  be having your list of numbers in an array. And then create the new array.

 

A recommended way to get reasonable random numbers is to have a title screen, because the random number generator is counting on each video frame, and once the user press start it will be a "random" time. So if you run this piece of code in emulation (or even in a real Intellivision), it will generate the same numbers every time unless you add a title screen.

 

DIM random_array(5)

 

CLS

 

' Needs to set array to zero so it can find free slots

FOR c = 0 TO 4

    random_array(c) = 0

NEXT c

 

filling = 0

DO

    number = my_favorite_numbers(filling)

    DO       ' Find a random non-used spot

        c = RANDOM(5)

    LOOP WHILE random_array(c) <> 0

    random_array(c) = number    ' Fill spot

    PRINT AT c * 20 COLOR 6,<>number    ' Debugging

    filling = filling + 1

LOOP WHILE filling < 5

 

WHILE 1: WEND     ' So we don't make CPU to run over the data

 

my_favorite_numbers: DATA 4, 12, 20, 15, 3