Question

我需要找到3个数组的解决方案，以解决a + b + c = 15（或其他问题）

到目前为止，我仍然坚持以下代码：

A = 1:10
B = 1:10
C = 1:10

possibilities = Iterators.product(A, B, C)
solutions = Iterators.filter((a, b, c) -> a + b + c == 15, possibilities)
sol = collect(solutions)
for (a, b, c) in sol
   println(a, " ", b, " ", c)
end

然后我从编译器收到此错误：

> ERROR: LoadError: MethodError: no method matching
> (::##1#2)(::Tuple{Int64,Int64,Int64}) Closest candidates are:  
> #1(::Any, !Matched::Any, !Matched::Any) at /home/cg/root/7729001/main.jl:6 Stacktrace:  [1] start_filter(::##1#2,
> ::Base.Iterators.Prod{UnitRange{Int64},Base.Iterators.Prod2{UnitRange{Int64},UnitRange{Int64}}})
> at ./iterators.jl:272  [2] _collect(::UnitRange{Int64},
> ::Base.Iterators.Filter{##1#2,Base.Iterators.Prod{UnitRange{Int64},Base.Iterators.Prod2{UnitRange{Int64},UnitRange{Int64}}}},
> ::Base.HasEltype, ::Base.SizeUnknown) at ./array.jl:408  [3]
> collect(::Base.Iterators.Filter{##1#2,Base.Iterators.Prod{UnitRange{Int64},Base.Iterators.Prod2{UnitRange{Int64},UnitRange{Int64}}}})
> at ./array.jl:397 while loading /home/cg/root/7729001/main.jl, in
> expression starting on line 7

也许您有解决此问题的方法或解决此问题的方法。

Answer 1

可能性的要素是元组。在此代码中，将每个都视为x：

A = 1:10
B = 1:10
C = 1:10

possibilities = Iterators.product(A, B, C)
# The change is in this line
solutions = Iterators.filter(x -> x[1] + x[2] + x[3] == 15, possibilities)
sol = collect(solutions)
for (a, b, c) in sol
   println(a, " ", b, " ", c)
end

Answer 2

另一个答案正确地诊断出您需要处理一个元组，而不是三个参数。

在Julia 1.0中，您也可以在lambda中使用argument destructuring，但是语法并不那么明显：

Iterators.filter(((a, b, c),) -> a + b + c == 15, possibilities)

Julia Iterator产品和过滤器

2 个答案: