Function malachite_base::vecs::exhaustive::exhaustive_unique_vecs_min_length

pub fn exhaustive_unique_vecs_min_length<I: Iterator>(
    min_length: u64,
    xs: I,
) -> ExhaustiveUniqueVecs<I> 
where
    I::Item: Clone,

Generates Vecs with a mininum length, 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 the input iterator is infinite, the output length is also infinite.

If the input iterator length is $n$ and the min_length is $\ell$, the output length is $$ \sum_ {k=\ell}^n \frac{n!}{k!}. $$

Examples

use itertools::Itertools;
use malachite_base::vecs::exhaustive::exhaustive_unique_vecs_min_length;

let xss = exhaustive_unique_vecs_min_length(2, 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]
    ]
);