Randomize a List problem

[Albert Chan]

(09-15-2020 03:57 PM)Hlib Wrote:  I inserted a fragment into the source program, which swaps 1-st and random n-th elements on stack ...

Do not use this code ! This is much worse than "random(t) ROLLD"

Code:

Starting pattern = 123, shuffled pattern has 3^3 = 27 ways

Pattern swap 1st random(t) ROLLD
123     7        5
132     2        4        
213     6        5
231     3        5
312     3        4
321     6        4

Uneven probabilities problem get worse with more items in the list.
This is not just pigeonhole issues anymore.

I would recommend not cutting corners here, and use good shuffling code.

Code:

Starting pattern = 1234, shuffled pattern has 4^4 = 256 ways

Pattern swap 1st random(t) ROLLD
1234    34       15
1243    8        7
1324    8        14
1342    3        14
1423    3        7
1432    8        7
2134    24       15
2143    4        7
2314    14       15
2341    4        15
2413    4        7
2431    14       7
3124    14       14
3142    4        14
3214    24       14
3241    14       14
3412    4        14
3421    4        14
4123    4        7
4132    14       7
4213    14       7
4231    24       7
4312    4        7
4321    4        7