Function malachite_base::sets::exhaustive::lex_b_tree_sets_length_range
source · [−]pub fn lex_b_tree_sets_length_range<I: Clone + Iterator>(
a: u64,
b: u64,
xs: I
) -> LexOrderedUniqueCollections<I, BTreeSet<I::Item>>ⓘNotable traits for LexOrderedUniqueCollections<I, C>impl<I: Iterator, C: FromIterator<I::Item>> Iterator for LexOrderedUniqueCollections<I, C> where
I::Item: Clone, type Item = C;
where
I::Item: Clone + Ord,
Expand description
Generates BTreeSet
s, with lengths in a range $[a, b)$, with elements from a single iterator.
The BTreeSet
s are ordered lexicographically with respect to the order of the element
iterator.
The source iterator should not repeat any elements, but this is not enforced.
The iterator should be finite; if it is infinite, only prefixes of the iterator will be generated.
If $a \leq b$, the output is empty.
If $a = 0$ and $b = 1$, the output consists of a single empty BTreeSet
.
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 $$ \sum_{i=a}^b - 1 \binom{n}{i}. $$
Examples
extern crate itertools;
#[macro_use]
extern crate maplit;
use itertools::Itertools;
use malachite_base::sets::exhaustive::lex_b_tree_sets_length_range;
fn main() {
let xss = lex_b_tree_sets_length_range(2, 4, 1..=4).collect_vec();
assert_eq!(
xss,
&[
btreeset!{1, 2},
btreeset!{1, 2, 3},
btreeset!{1, 2, 4},
btreeset!{1, 3},
btreeset!{1, 3, 4},
btreeset!{1, 4},
btreeset!{2, 3},
btreeset!{2, 3, 4},
btreeset!{2, 4},
btreeset!{3, 4},
]
);
}