[section:nth_element nth_element]

[heading Prototype]

``
template<class RandomAccessRange>
RandomAccessRange& nth_element(
    RandomAccessRange& rng,
    typename range_iterator<RandomAccessRange>::type nth);

template<class RandomAccessRange>
const RandomAccessRange& nth_element(
    const RandomAccessRange& rng,
    typename range_iterator<const RandomAccessRange>::type nth);

template<class RandomAccessRange>
RandomAccessRange& nth_element(
    RandomAccessRange& rng,
    typename range_iterator<RandomAccessRange>::type nth,
    BinaryPredicate sort_pred);

template<class RandomAccessRange>
const RandomAccessRange& nth_element(
    const RandomAccessRange& rng,
    typename range_iterator<const RandomAccessRange>::type nth,
    BinaryPredicate sort_pred);
``

[heading Description]

`nth_element` partially orders a range of elements. `nth_element` arranges the range `rng` such that the element corresponding with the iterator `nth` is the same as the element that would be in that position if `rng` has been sorted.


[heading Definition]

Defined in the header file `boost/range/algorithm/nth_element.hpp`

[heading Requirements]

[*For the non-predicate version:]

* `RandomAccessRange` is a model of the __random_access_range__ Concept.
* `RandomAccessRange` is mutable.
* `RandomAccessRange`'s value type is a model of the `LessThanComparableConcept`.
* The ordering relation on `RandomAccessRange`'s value type is a [*/strict weak ordering/], as defined in the `LessThanComparableConcept` requirements.


[*For the predicate version:]

* `RandomAccessRange` is a model of the __random_access_range__ Concept.
* `RandomAccessRange` is mutable.
* `BinaryPredicate` is a model of the `StrictWeakOrderingConcept`.
* `RandomAccessRange`'s value type is convertible to both of `BinaryPredicate`'s argument types.


[heading Complexity]

On average, linear in `distance(rng)`.

[endsect]