subsets的算法是怎么样的
我想用fortran实现mathematica里subset的功能。就是算出所有包含k个元素的子数列。有谁知道怎么处理吗? 先谢过了 subsets := {{}};subsets[{}, k_] := {};
subsets[{x_, xs___}, k_] :=
Table[{x}~Join~i, {i, subsets[{xs}, k - 1]}]~Join~subsets[{xs}, k];
subsets, 3] == Subsets, {3}]
Sort@Fold[#~Join~Table &, {{}}, Range] ==
Subsets]
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