Boustrophedon transform: Difference between revisions
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!@x: b 15
1 2 5 17 73 381 2347 16701 134993 1222873 12279251 135425553 1627809401 21183890469 296773827547</syntaxhighlight>
=== Alternate implementation ===
Instead of relying on recursion and memoization, we can deliberately perform the operations in the correct order:
<syntaxhighlight lang=J>B=: {{
M=: |:y#,:u i.y
for_i.(#~>:/"1)1+(,#:i.@*)~y-1 do.
M=:M (<i)}~(M{~<i-0 1)+M{~<(-/\i)-1 0
end.
M|:~<1 0
}}</syntaxhighlight>
Here, we start with a square matrix with the <code>a</code> values in sequence in the first column (first line). Then we fill in the remaining needed <code>T</code> values in row major order (for loop). Finally, we extract the diagonal (last line). Usage and results are the same as before.
=={{header|Julia}}==
<syntaxhighlight lang="julia">using Primes
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