pub fn exhaustive_unique_vecs_length_range<I: Iterator>(
a: u64,
b: u64,
xs: I
) -> ExhaustiveUniqueVecs<I> ⓘwhere
I::Item: Clone,Expand description
Generates Vecs, with lengths in a range $[a, b)$, with elements from a single iterator,
such that each Vec has no repeated elements.
The source iterator should not repeat any elements, but this is not enforced.
If $a \leq b$, the output is empty.
If $a = 0$ and $b = 1$, the output consists of a single empty Vec.
If the input iterator is infinite and $0 < a < b$, the output length is also infinite.
If the input iterator length is $n$, the output length is $$ \sum_{i=a}^{b - 1} \frac{n!}{k!}. $$
Examples
use itertools::Itertools;
use malachite_base::vecs::exhaustive::exhaustive_unique_vecs_length_range;
let xss = exhaustive_unique_vecs_length_range(2, 4, 1..=4).take(20).collect_vec();
assert_eq!(
xss.iter().map(Vec::as_slice).collect_vec().as_slice(),
&[
&[1, 2][..],
&[1, 3],
&[2, 1],
&[2, 3],
&[3, 1],
&[3, 2],
&[1, 2, 3],
&[1, 2, 4],
&[1, 3, 2],
&[1, 4],
&[2, 1, 3],
&[2, 4],
&[2, 3, 1],
&[4, 1],
&[3, 1, 2],
&[3, 4],
&[3, 2, 1],
&[4, 2],
&[1, 4, 2],
&[1, 3, 4]
]
);