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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 19:14, 15 June 2022
, 1 year ago→{{header|Lua}}: added another Lua solution
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end
end</lang>
=== Functional-esque (non-iterator) ===
Motivation: If a list-of-lists is passed into the cartesian product, then wouldn't a list-of-lists be the expected return type? Of course this is just personal opinion/preference, other implementations are fine as-is if you'd rather have an iterator.
<lang lua>-- support:
function T(t) return setmetatable(t, {__index=table}) end
table.clone = function(t) local s=T{} for k,v in ipairs(t) do s[k]=v end return s end
table.reduce = function(t,f,acc) for i=1,#t do acc=f(t[i],acc) end return acc end
-- implementation:
local function cartprod(sets)
local temp, prod = T{}, T{}
local function descend(depth)
for _,v in ipairs(sets[depth]) do
temp[depth] = v
if (depth==#sets) then prod[#prod+1]=temp:clone() else descend(depth+1) end
end
end
descend(1)
return prod
end
-- demonstration:
tests = {
{ {1, 2}, {3, 4} },
{ {3, 4}, {1, 2} },
{ {1, 2}, {} },
{ {}, {1, 2} },
{ {1776, 1789}, {7, 12}, {4, 14, 23}, {0, 1} },
{ {1, 2, 3}, {30}, {500, 100} },
{ {1, 2, 3}, {}, {500, 100} }
}
for _,test in ipairs(tests) do
local cp = cartprod(test)
print("{"..cp:reduce(function(t,a) return (a=="" and a or a..", ").."("..t:concat(", ")..")" end,"").."}")
end</lang>
{{out}}
<pre>{(1, 3), (1, 4), (2, 3), (2, 4)}
{(3, 1), (3, 2), (4, 1), (4, 2)}
{}
{}
{(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)}
{(1, 30, 500), (1, 30, 100), (2, 30, 500), (2, 30, 100), (3, 30, 500), (3, 30, 100)}
{}</pre>
=={{header|Maple}}==
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