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De Bruijn sequences: Difference between revisions
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=={{header|J}}==
<lang J>NB. implement inverse Burrows—Wheeler transform sequence method
repeat_alphabet=: [: , [: i.&> (^ <:) # [
assert 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 -: 2 repeat_alphabet 4
de_bruijn=: ({~ ([: ; [: C. /:^:2))@:repeat_alphabet NB. K de_bruijn N
pins=: #&10 #: [: i. 10&^ NB. pins y generates all y digit PINs
groups=: [ ]\ ] , ({.~ <:)~ NB. x infixes of sequence cyclically extended by x-1
verify_PINs=: (/:~@:groups -: pins@:[) NB. LENGTH verify_PINs SEQUENCE
</lang><pre> NB. A is the sequence
A=: 10 de_bruijn 4
NB. tally A
#A
10000
NB. literally the first and final 130 digits
Num_j_ {~ 130 ({. ,: ({.~ -)~) A
0000101001101111000210020102110202001210120112111202121200221022012211220222122220003100320030103110321030203120322030300131013201
9469956996699769986990799179927993799479957996799779987990899189928993899489958996899789988990999199929993999499959996999799989999
NB. verifications. seriously?
4 verify_PINs A
1
4 (verify_PINs |.) A
1
4 verify_PINs (a.i.'.')(<: 4444)} A
0
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=={{header|Java}}==
{{trans|C++}}
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