Consider the problem of sorting the first n elements of a given vector.
The function std::partial_sort from the C++ STL does just this.

An alternate implementation of a partial sort algorithm is to use
std::nth_element to partition the given vector at the nth sorted
element and then use std::sort, both from the STL, to sort the vector
from the beginning to the nth element.

For an equivalent implementation in R, we can use the sort function by
specifying a vector of 1:n for the partial argument (i.e. partial=1:n).

An interesting result to note is the gain in speed of
nth_partial_sort over stl_partial_sort. In this case, for the given
data, it is faster to use the combination ofstd::nth_element and
std::sort rather than std::partial_sort to sort the first n elements
of a vector.

Finally, consider a problem where you only need a single element of a
sorted vector. The function std::nth_element from the C++ STL does just
this. An example of this type of problem is computing the median of a given
vector.

For an equivalent implementation in R, we can use the sort function by
specifying a scalar value for the argument partial (i.e. partial=n).

While these are not huge speed improvements over the base R sort function,
this post demonstrates how to easily access sorting functions in the C++
STL and is a good exercise to better understand the differences and
performance of the sorting algorithms available in C++ and R.