wolfram-mathematica - 列表的顺序子集

Question

给出一个列表说

{"a", "b", "c", "d"}

有没有更简单的方法来生成这样的顺序子集列表(结果的顺序并不重要)

{
 {"a"},
 {"a b"},
 {"a b c"},
 {"a b c d"},
 {"b"},
 {"b c"},
 {"b c d"},
 {"c"},
 {"c d"},
 {"d"}
}

Answer 1

我想我最喜欢这个:

set = {"a", "b", "c", "d"};

ReplaceList[set, {___, x__, ___} :> {x}]

随着字符串加入:

ReplaceList[set, {___, x__, ___} :> "" <> Riffle[{x}, " "]]

以类似的方式，特定于字符串:

StringCases["abcd", __, Overlaps -> All]

由于 Nasser 说我在作弊，这里有一个更手动的方法，它在大型集合上也有更高的效率:

ClearAll[f, f2]
f[i_][x_] := NestList[i, x, Length@x - 1]
f2[set_]  := Join @@ ( f[Most] /@ f[Rest][set] )

f2[{"a", "b", "c", "d"}]