C++ sorting and keeping track of indexes

Question

Using C++, and hopefully the standard library, I want to sort a sequence of samples in ascending order, but I also want to remember the original indexes of the new samples.<

Answer 1

Make a std::pair in function then sort pair :

generic version :

template< class RandomAccessIterator,class Compare >
auto sort2(RandomAccessIterator begin,RandomAccessIterator end,Compare cmp) ->
   std::vector>
{
    using valueType=typename std::iterator_traits::value_type;
    using Pair=std::pair;

    std::vector index_pair;
    index_pair.reserve(std::distance(begin,end));

    for(uint32_t idx=0;begin!=end;++begin,++idx){
        index_pair.push_back(Pair(idx,begin));
    }

    std::sort( index_pair.begin(),index_pair.end(),[&](const Pair& lhs,const Pair& rhs){
          return cmp(*lhs.second,*rhs.second);
    });

    return index_pair;
}

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