24 lines
586 B
Text
24 lines
586 B
Text
split:{1_'(&x=y)_ x:y,x}
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g: ("ABCD CABD ACDB DACB BCDA ACBD ADCB CDAB DABC BCAD CADB")
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g,:(" CDBA CBAD ABDC ADBC BDCA DCBA BACD BADC BDAC CBDA DBCA DCAB")
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p: split[g;" "];
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/ All permutations of "ABCD"
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perm:{:[1<x;,/(>:'(x,x)#1,x#0)[;0,'1+_f x-1];,!x]}
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p2:a@(perm(#a:"ABCD"));
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/ Which permutations in p are there in p2?
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p2 _lin p
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1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1
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/ Invert the result
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~p2 _lin p
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
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/ It's the 20th permutation that is missing
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&~p2 _lin p
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,20
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p2@&~p2 _lin p
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"DBAC"
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