template <RandomAccessIterator I, Sentinel<I> S, class Comp = less<>,
class Proj = identity>
requires Sortable<I, Comp, Proj>
I stable_sort(I first, S last, Comp comp = Comp{}, Proj proj = Proj{});
template <RandomAccessRange Rng, class Comp = less<>, class Proj = identity>
requires Sortable<iterator_t<Rng>, Comp, Proj>
safe_iterator_t<Rng>
stable_sort(Rng&& rng, Comp comp = Comp{}, Proj proj = Proj{});
Effects: Sorts the elements in the range [first,last).
Returns: last.
Complexity: Let N == last - first. If enough extra memory is available, N log(N) comparisons. Otherwise, at most N log2(N) comparisons. In either case, twice as many applications of the projection as the number of comparisons.
Remarks: Stable ( ISO/IEC 14882:2014 §[algorithm.stable]).