1) Finds the smallest and largest elements in the range [first, last).
2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.
The function-like entities described on this page are
(informally known as niebloids), that is:
An object consisting of an iterator to the smallest element as the first element and an iterator to the greatest element as the second. Returns {first,first} if the range is empty. If several elements are equivalent to the smallest element, the iterator to the first such element is returned. If several elements are equivalent to the largest element, the iterator to the last such element is returned.
At most std::max(std::floor(1.5*(N−1)),0.0) applications of the comparison and twice as many applications of the projection, where N=ranges::distance(first,last).
structminmax_element_fn{template<std::forward_iteratorI,std::sentinel_for<I>S,classProj=std::identity,std::indirect_strict_weak_order<std::projected<I,Proj>>Comp=ranges::less>constexprranges::minmax_element_result<I>operator()(Ifirst,Slast,Compcomp={},Projproj={})const{automin=first,max=first;if(first==last||++first==last)return{min,max};if(std::invoke(comp,std::invoke(proj,*first),std::invoke(proj,*min)))min=first;elsemax=first;while(++first!=last){autoi=first;if(++first==last){if(std::invoke(comp,std::invoke(proj,*i),std::invoke(proj,*min)))min=i;elseif(!(std::invoke(comp,std::invoke(proj,*i),std::invoke(proj,*max))))max=i;break;}else{if(std::invoke(comp,std::invoke(proj,*first),std::invoke(proj,*i))){if(std::invoke(comp,std::invoke(proj,*first),std::invoke(proj,*min)))min=first;if(!(std::invoke(comp,std::invoke(proj,*i),std::invoke(proj,*max))))max=i;}else{if(std::invoke(comp,std::invoke(proj,*i),std::invoke(proj,*min)))min=i;if(!(std::invoke(comp,std::invoke(proj,*first),std::invoke(proj,*max))))max=first;}}}return{min,max};}template<ranges::forward_rangeR,classProj=std::identity,std::indirect_strict_weak_order<std::projected<ranges::iterator_t<R>,Proj>>Comp=ranges::less>constexprranges::minmax_element_result<ranges::borrowed_iterator_t<R>>operator()(R&&r,Compcomp={},Projproj={})const{return(*this)(ranges::begin(r),ranges::end(r),std::ref(comp),std::ref(proj));}};inlineconstexprminmax_element_fnminmax_element;Run this code
#include<algorithm>#include<iostream>#include<iterator>namespaceranges=std::ranges;intmain(){constautov={3,9,1,4,1,2,5,9};constauto[min,max]=ranges::minmax_element(v);std::cout<<"min = "<<*min<<", at ["<<ranges::distance(v.begin(),min)<<"]\n"<<"max = "<<*max<<", at ["<<ranges::distance(v.begin(),max)<<"]\n";}Output:
min = 1, at [2] max = 9, at [7]