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Cartesian product of two or more lists: Difference between revisions
Cartesian product of two or more lists (view source)
Revision as of 04:12, 14 December 2020
, 3 years agoAdded Crystal implementation
(Added Crystal implementation) |
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NIL
</lang>
=={{header|Crystal}}==
The first function is the basic task. The version overloaded for one argument is the extra credit task, implemented using recursion.
<lang crystal>def cartesian_product(a, b)
return a.flat_map { |i| b.map { |j| [i, j] } }
end
def cartesian_product(l)
if l.size <= 1
return l
elsif l.size == 2
return cartesian_product(l[0], l[1])
end
return l[0].flat_map { |i|
cartesian_product(l[1..]).map { |j|
[i, j].flatten
}
}
end
tests = [ [[1, 2], [3, 4]],
[[3, 4], [1, 2]],
[[1, 2], [] of Int32],
[[] of Int32, [1, 2]],
[[1, 2, 3], [30], [500, 100]],
[[1, 2, 3], [] of Int32, [500, 100]],
[[1776, 1789], [7, 12], [4, 14, 23], [0, 1]] ]
tests.each { |test|
puts "#{test.join(" x ")} ->"
puts " #{cartesian_product(test)}"
puts ""
}
</lang>
{{out}}
<pre>[1, 2] x [3, 4] ->
[[1, 3], [1, 4], [2, 3], [2, 4]]
[3, 4] x [1, 2] ->
[[3, 1], [3, 2], [4, 1], [4, 2]]
[1, 2] x [] ->
[]
[] x [1, 2] ->
[]
[1, 2, 3] x [30] x [500, 100] ->
[[1, 30, 500], [1, 30, 100], [2, 30, 500], [2, 30, 100], [3, 30, 500], [3, 30, 100]]
[1, 2, 3] x [] x [500, 100] ->
[]
[1776, 1789] x [7, 12] x [4, 14, 23] x [0, 1] ->
[[1776, 7, 4, 0], [1776, 7, 4, 1], [1776, 7, 14, 0], [1776, 7, 14, 1], [1776, 7, 23, 0], [1776, 7, 23, 1], [1776, 12, 4, 0], [1776, 12, 4, 1], [1776, 12, 14, 0], [1776, 12, 14, 1], [1776, 12, 23, 0], [1776, 12, 23, 1], [1789, 7, 4, 0], [1789, 7, 4, 1], [1789, 7, 14, 0], [1789, 7, 14, 1], [1789, 7, 23, 0], [1789, 7, 23, 1], [1789, 12, 4, 0], [1789, 12, 4, 1], [1789, 12, 14, 0], [1789, 12, 14, 1], [1789, 12, 23, 0], [1789, 12, 23, 1]]
</pre>
=={{header|D}}==
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