Struct std::collections::BTreeSet

pub struct BTreeSet<T> { /* fields omitted */ }

A set based on a B-Tree.

See BTreeMap’s documentation for a detailed discussion of this collection’s performance benefits and drawbacks.

It is a logic error for an item to be modified in such a way that the item’s ordering relative to any other item, as determined by the Ord trait, changes while it is in the set. This is normally only possible through Cell, RefCell, global state, I/O, or unsafe code. The behavior resulting from such a logic error is not specified, but will not result in undefined behavior. This could include panics, incorrect results, aborts, memory leaks, and non-termination.

Examples

use std::collections::BTreeSet;

// Type inference lets us omit an explicit type signature (which
// would be `BTreeSet<&str>` in this example).
let mut books = BTreeSet::new();

// Add some books.
books.insert("A Dance With Dragons");
books.insert("To Kill a Mockingbird");
books.insert("The Odyssey");
books.insert("The Great Gatsby");

// Check for a specific one.
if !books.contains("The Winds of Winter") {
    println!("We have {} books, but The Winds of Winter ain't one.",
             books.len());
}

// Remove a book.
books.remove("The Odyssey");

// Iterate over everything.
for book in &books {
    println!("{}", book);
}

A BTreeSet with a known list of items can be initialized from an array:

use std::collections::BTreeSet;

let set = BTreeSet::from([1, 2, 3]);

Implementations

Makes a new, empty BTreeSet.

Does not allocate anything on its own.

Examples

use std::collections::BTreeSet;

let mut set: BTreeSet<i32> = BTreeSet::new();
Notable traits for Range<'a, T>
impl<'a, T> Iterator for Range<'a, T>
    type Item = &'a T;

Constructs a double-ended iterator over a sub-range of elements in the set. The simplest way is to use the range syntax min..max, thus range(min..max) will yield elements from min (inclusive) to max (exclusive). The range may also be entered as (Bound<T>, Bound<T>), so for example range((Excluded(4), Included(10))) will yield a left-exclusive, right-inclusive range from 4 to 10.

Examples

use std::collections::BTreeSet;
use std::ops::Bound::Included;

let mut set = BTreeSet::new();
set.insert(3);
set.insert(5);
set.insert(8);
for &elem in set.range((Included(&4), Included(&8))) {
    println!("{}", elem);
}
assert_eq!(Some(&5), set.range(4..).next());
Notable traits for Difference<'a, T>
impl<'a, T> Iterator for Difference<'a, T> where
    T: Ord, 
    type Item = &'a T;

Visits the values representing the difference, i.e., the values that are in self but not in other, in ascending order.

Examples

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);

let mut b = BTreeSet::new();
b.insert(2);
b.insert(3);

let diff: Vec<_> = a.difference(&b).cloned().collect();
assert_eq!(diff, [1]);
Notable traits for SymmetricDifference<'a, T>
impl<'a, T> Iterator for SymmetricDifference<'a, T> where
    T: Ord, 
    type Item = &'a T;

Visits the values representing the symmetric difference, i.e., the values that are in self or in other but not in both, in ascending order.

Examples

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);

let mut b = BTreeSet::new();
b.insert(2);
b.insert(3);

let sym_diff: Vec<_> = a.symmetric_difference(&b).cloned().collect();
assert_eq!(sym_diff, [1, 3]);
Notable traits for Intersection<'a, T>
impl<'a, T> Iterator for Intersection<'a, T> where
    T: Ord, 
    type Item = &'a T;

Visits the values representing the intersection, i.e., the values that are both in self and other, in ascending order.

Examples

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);

let mut b = BTreeSet::new();
b.insert(2);
b.insert(3);

let intersection: Vec<_> = a.intersection(&b).cloned().collect();
assert_eq!(intersection, [2]);
Notable traits for Union<'a, T>
impl<'a, T> Iterator for Union<'a, T> where
    T: Ord, 
    type Item = &'a T;

Visits the values representing the union, i.e., all the values in self or other, without duplicates, in ascending order.

Examples

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);

let mut b = BTreeSet::new();
b.insert(2);

let union: Vec<_> = a.union(&b).cloned().collect();
assert_eq!(union, [1, 2]);

Clears the set, removing all values.

Examples

use std::collections::BTreeSet;

let mut v = BTreeSet::new();
v.insert(1);
v.clear();
assert!(v.is_empty());

Returns true if the set contains a value.

The value may be any borrowed form of the set’s value type, but the ordering on the borrowed form must match the ordering on the value type.

Examples

use std::collections::BTreeSet;

let set: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.contains(&1), true);
assert_eq!(set.contains(&4), false);

Returns a reference to the value in the set, if any, that is equal to the given value.

The value may be any borrowed form of the set’s value type, but the ordering on the borrowed form must match the ordering on the value type.

Examples

use std::collections::BTreeSet;

let set: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.get(&2), Some(&2));
assert_eq!(set.get(&4), None);

Returns true if self has no elements in common with other. This is equivalent to checking for an empty intersection.

Examples

use std::collections::BTreeSet;

let a: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
let mut b = BTreeSet::new();

assert_eq!(a.is_disjoint(&b), true);
b.insert(4);
assert_eq!(a.is_disjoint(&b), true);
b.insert(1);
assert_eq!(a.is_disjoint(&b), false);

Returns true if the set is a subset of another, i.e., other contains at least all the values in self.

Examples

use std::collections::BTreeSet;

let sup: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
let mut set = BTreeSet::new();

assert_eq!(set.is_subset(&sup), true);
set.insert(2);
assert_eq!(set.is_subset(&sup), true);
set.insert(4);
assert_eq!(set.is_subset(&sup), false);

Returns true if the set is a superset of another, i.e., self contains at least all the values in other.

Examples

use std::collections::BTreeSet;

let sub: BTreeSet<_> = [1, 2].iter().cloned().collect();
let mut set = BTreeSet::new();

assert_eq!(set.is_superset(&sub), false);

set.insert(0);
set.insert(1);
assert_eq!(set.is_superset(&sub), false);

set.insert(2);
assert_eq!(set.is_superset(&sub), true);
???? This is a nightly-only experimental API. (map_first_last #62924)

Returns a reference to the first value in the set, if any. This value is always the minimum of all values in the set.

Examples

Basic usage:

#![feature(map_first_last)]
use std::collections::BTreeSet;

let mut set = BTreeSet::new();
assert_eq!(set.first(), None);
set.insert(1);
assert_eq!(set.first(), Some(&1));
set.insert(2);
assert_eq!(set.first(), Some(&1));
???? This is a nightly-only experimental API. (map_first_last #62924)

Returns a reference to the last value in the set, if any. This value is always the maximum of all values in the set.

Examples

Basic usage:

#![feature(map_first_last)]
use std::collections::BTreeSet;

let mut set = BTreeSet::new();
assert_eq!(set.last(), None);
set.insert(1);
assert_eq!(set.last(), Some(&1));
set.insert(2);
assert_eq!(set.last(), Some(&2));
???? This is a nightly-only experimental API. (map_first_last #62924)

Removes the first value from the set and returns it, if any. The first value is always the minimum value in the set.

Examples

#![feature(map_first_last)]
use std::collections::BTreeSet;

let mut set = BTreeSet::new();

set.insert(1);
while let Some(n) = set.pop_first() {
    assert_eq!(n, 1);
}
assert!(set.is_empty());
???? This is a nightly-only experimental API. (map_first_last #62924)

Removes the last value from the set and returns it, if any. The last value is always the maximum value in the set.

Examples

#![feature(map_first_last)]
use std::collections::BTreeSet;

let mut set = BTreeSet::new();

set.insert(1);
while let Some(n) = set.pop_last() {
    assert_eq!(n, 1);
}
assert!(set.is_empty());

Adds a value to the set.

If the set did not have this value present, true is returned.

If the set did have this value present, false is returned, and the entry is not updated. See the module-level documentation for more.

Examples

use std::collections::BTreeSet;

let mut set = BTreeSet::new();

assert_eq!(set.insert(2), true);
assert_eq!(set.insert(2), false);
assert_eq!(set.len(), 1);

Adds a value to the set, replacing the existing value, if any, that is equal to the given one. Returns the replaced value.

Examples

use std::collections::BTreeSet;

let mut set = BTreeSet::new();
set.insert(Vec::<i32>::new());

assert_eq!(set.get(&[][..]).unwrap().capacity(), 0);
set.replace(Vec::with_capacity(10));
assert_eq!(set.get(&[][..]).unwrap().capacity(), 10);

Removes a value from the set. Returns whether the value was present in the set.

The value may be any borrowed form of the set’s value type, but the ordering on the borrowed form must match the ordering on the value type.

Examples

use std::collections::BTreeSet;

let mut set = BTreeSet::new();

set.insert(2);
assert_eq!(set.remove(&2), true);
assert_eq!(set.remove(&2), false);

Removes and returns the value in the set, if any, that is equal to the given one.

The value may be any borrowed form of the set’s value type, but the ordering on the borrowed form must match the ordering on the value type.

Examples

use std::collections::BTreeSet;

let mut set: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
assert_eq!(set.take(&2), Some(2));
assert_eq!(set.take(&2), None);

Retains only the elements specified by the predicate.

In other words, remove all elements e such that f(&e) returns false. The elements are visited in ascending order.

Examples

use std::collections::BTreeSet;

let xs = [1, 2, 3, 4, 5, 6];
let mut set: BTreeSet<i32> = xs.iter().cloned().collect();
// Keep only the even numbers.
set.retain(|&k| k % 2 == 0);
assert!(set.iter().eq([2, 4, 6].iter()));

Moves all elements from other into Self, leaving other empty.

Examples

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);
a.insert(3);

let mut b = BTreeSet::new();
b.insert(3);
b.insert(4);
b.insert(5);

a.append(&mut b);

assert_eq!(a.len(), 5);
assert_eq!(b.len(), 0);

assert!(a.contains(&1));
assert!(a.contains(&2));
assert!(a.contains(&3));
assert!(a.contains(&4));
assert!(a.contains(&5));

Splits the collection into two at the given value. Returns everything after the given value, including the value.

Examples

Basic usage:

use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);
a.insert(3);
a.insert(17);
a.insert(41);

let b = a.split_off(&3);

assert_eq!(a.len(), 2);
assert_eq!(b.len(), 3);

assert!(a.contains(&1));
assert!(a.contains(&2));

assert!(b.contains(&3));
assert!(b.contains(&17));
assert!(b.contains(&41));
Notable traits for DrainFilter<'_, T, F>
impl<'a, '_, T, F> Iterator for DrainFilter<'_, T, F> where
    F: 'a + FnMut(&T) -> bool, 
    type Item = T;
???? This is a nightly-only experimental API. (btree_drain_filter #70530)

Creates an iterator that visits all values in ascending order and uses a closure to determine if a value should be removed.

If the closure returns true, the value is removed from the set and yielded. If the closure returns false, or panics, the value remains in the set and will not be yielded.

If the iterator is only partially consumed or not consumed at all, each of the remaining values is still subjected to the closure and removed and dropped if it returns true.

It is unspecified how many more values will be subjected to the closure if a panic occurs in the closure, or if a panic occurs while dropping a value, or if the DrainFilter itself is leaked.

Examples

Splitting a set into even and odd values, reusing the original set:

#![feature(btree_drain_filter)]
use std::collections::BTreeSet;

let mut set: BTreeSet<i32> = (0..8).collect();
let evens: BTreeSet<_> = set.drain_filter(|v| v % 2 == 0).collect();
let odds = set;
assert_eq!(evens.into_iter().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 7]);
Notable traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
    type Item = &'a T;

Gets an iterator that visits the values in the BTreeSet in ascending order.

Examples

use std::collections::BTreeSet;

let set: BTreeSet<usize> = [1, 2, 3].iter().cloned().collect();
let mut set_iter = set.iter();
assert_eq!(set_iter.next(), Some(&1));
assert_eq!(set_iter.next(), Some(&2));
assert_eq!(set_iter.next(), Some(&3));
assert_eq!(set_iter.next(), None);

Values returned by the iterator are returned in ascending order:

use std::collections::BTreeSet;

let set: BTreeSet<usize> = [3, 1, 2].iter().cloned().collect();
let mut set_iter = set.iter();
assert_eq!(set_iter.next(), Some(&1));
assert_eq!(set_iter.next(), Some(&2));
assert_eq!(set_iter.next(), Some(&3));
assert_eq!(set_iter.next(), None);

Returns the number of elements in the set.

Examples

use std::collections::BTreeSet;

let mut v = BTreeSet::new();
assert_eq!(v.len(), 0);
v.insert(1);
assert_eq!(v.len(), 1);

Returns true if the set contains no elements.

Examples

use std::collections::BTreeSet;

let mut v = BTreeSet::new();
assert!(v.is_empty());
v.insert(1);
assert!(!v.is_empty());

Trait Implementations

Returns the intersection of self and rhs as a new BTreeSet<T>.

Examples

use std::collections::BTreeSet;

let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();

let result = &a & &b;
let result_vec: Vec<_> = result.into_iter().collect();
assert_eq!(result_vec, [2, 3]);

The resulting type after applying the & operator.

Returns the union of self and rhs as a new BTreeSet<T>.

Examples

use std::collections::BTreeSet;

let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();

let result = &a | &b;
let result_vec: Vec<_> = result.into_iter().collect();
assert_eq!(result_vec, [1, 2, 3, 4, 5]);

The resulting type after applying the | operator.

Returns the symmetric difference of self and rhs as a new BTreeSet<T>.

Examples

use std::collections::BTreeSet;

let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();

let result = &a ^ &b;
let result_vec: Vec<_> = result.into_iter().collect();
assert_eq!(result_vec, [1, 4]);

The resulting type after applying the ^ operator.

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Creates an empty BTreeSet.

Extends a collection with the contents of an iterator. Read more

???? This is a nightly-only experimental API. (extend_one #72631)

Extends a collection with exactly one element.

???? This is a nightly-only experimental API. (extend_one #72631)

Reserves capacity in a collection for the given number of additional elements. Read more

Extends a collection with the contents of an iterator. Read more

???? This is a nightly-only experimental API. (extend_one #72631)

Extends a collection with exactly one element.

???? This is a nightly-only experimental API. (extend_one #72631)

Reserves capacity in a collection for the given number of additional elements. Read more

use std::collections::BTreeSet;

let set1 = BTreeSet::from([1, 2, 3, 4]);
let set2: BTreeSet<_> = [1, 2, 3, 4].into();
assert_eq!(set1, set2);

Creates a value from an iterator. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Notable traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
    type Item = &'a T;

Creates an iterator from a value. Read more

Notable traits for IntoIter<T>
impl<T> Iterator for IntoIter<T>
    type Item = T;

Gets an iterator for moving out the BTreeSet’s contents.

Examples

use std::collections::BTreeSet;

let set: BTreeSet<usize> = [1, 2, 3, 4].iter().cloned().collect();

let v: Vec<_> = set.into_iter().collect();
assert_eq!(v, [1, 2, 3, 4]);

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Returns the difference of self and rhs as a new BTreeSet<T>.

Examples

use std::collections::BTreeSet;

let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();

let result = &a - &b;
let result_vec: Vec<_> = result.into_iter().collect();
assert_eq!(result_vec, [1, 2]);

The resulting type after applying the - operator.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

???? This is a nightly-only experimental API. (toowned_clone_into #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/collections/struct.BTreeSet.html