std::map Initialization Questions [Closed]

#include<iostream>
# include <map>
# include <string>
# include <vector>
# include <chrono>
using namespace std;
using namespace std::chrono;
structureKeyGenerator {
    using input_type=int;
    using value_type=string;
    static value_type generate (input_type i) {return to_string(i);}
};
template<typename OriginalIterator, typename Generator>
structure pair_generator_iterator{
    using original_value_type = typename OriginalIterator::value_type;
    using key_type = typename Generator::value_type;
    usingiterator_category = input_iterator_tag;
    using difference_type=int;
    using value_type=pair<key_type,original_value_type>;
    using pointer = value_type*;
    using reference=value_type&;
    pair_generator_iterator(OriginalIterator):_iter {iter} {}
    value_type operator*()const{
        original_value_type v=*_iter;
        return make_pair(KeyGenerator::generate(v),v);
    }
    pair_generator_iterator&operator++(){_iter++;return*this;}  
    friend bool operator==(const pair_generator_iterator&a, const pair_generator_iterator&b) {return a._iter==b._iter;}
    friend bool operator!=(const pair_generator_iterator&a, const pair_generator_iterator&b) {return!(a==b);}
private:
    OriginalIterator_iter;
};
int check_map(const map<string, int>&m){
    int total = 0;
    for(const auto&e:m){
        total + = e.first.length() + e.second;
    }
    return total;
}
int construct_table_with_iterator(constructor<int>&iv){
    map<string, int>m(
        pair_generator_iterator<vector<int>::const_iterator, KeyGenerator>(iv.begin()) ,
        pair_generator_iterator<vector<int>:const_iterator, KeyGenerator>(iv.end()));
    return check_map(m);
}
int construct_table_with_move(constructor<int>&iv){
    map<string, int>_m;
    for(inti=0;i<iv.size();++i){
        _m [to_string(i)] = i;
    }
    map<string, int>m=move(_m);
    return check_map(m);
}
int main() {
    constint N = 1000000;
    vector<int>iv(N);
    for(inti=0;i<N;++i){
        iv[i] = i;
    }
    auto p1 = chrono::high_resolution_clock::now();
    auto result1 = construct_table_with_iterator(iv);
    auto p2 = chrono::high_resolution_clock::now();
    auto p3 = chrono::high_resolution_clock::now();
    auto result2=construct_table_with_move(iv);
    auto p4 = chrono::high_resolution_clock::now();
    cout<<"iterator generator:"<duration_cast<microseconds>(p2-p1).count()<endl;
    cout<<"move:"<duration_cast<microseconds>(p4-p3).count()<endl;
    return result1!=result2;
}