Отсортировать вектор

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
template<typename T, typename RIT1, typename RIT2>
struct my_iter
{
    size_t index;
    RIT1 it1;
    RIT2 it2;
    my_iter operator +(const size_t d)const{return my_iter{index+d, it1, it2};}
    my_iter operator -(const size_t d)const{return my_iter{index-d, it1, it2};}
    size_t operator -(const my_iter& d)const{return index-d.index;}
    my_iter& operator++(){++index; return *this;}
    my_iter operator++(int){++index; return *this-1;}
    bool operator==(const my_iter& other)const{return index==other.index;}
    bool operator!=(const my_iter& other)const{return !(*this==other);}
    const T& operator*()const{return std::min(*(it1+index), *(it2+index));}
};
 
int main()
{
    std::vector<int> arr = {1,5,7,9,2,7,6,12};
    using t1 = decltype(arr.begin());
    using t2 = decltype(arr.rbegin());
    auto it = my_iter<int, t1, t2>{0,arr.begin(),arr.rbegin()};
    std::cout<<"Answer: "<<*std::max_element(it, it + arr.size()/2)<<std::endl;
}