Как ускорить работу с файлами?

#include <iostream>
#include <string>
#include <stdlib.h> //atoi))
#include <vector>
#include <fstream>
#include <windows.h>
using namespace std;
 
template<typename T>
void show_vec( vector<T> &vec, string name="")
{
if(name!="")cout<<name<<endl;
if(vec.size()>0)
for(size_t i=0; i<vec.size(); ++i)cout<<vec[i]<<' ';
cout<<endl;
}
template<typename T>
void show_vec( vector<pair<T,T>> &vec, string name="")
{
if(name!="")cout<<name<<endl;
if(vec.size()>0)
for(size_t i=0; i<vec.size(); ++i)cout<<vec[i].first<<' '<<vec[i].second<<endl;
cout<<endl;
}
 
void save_inp_tofile(string filename, vector<string> inp_vec)
{
ofstream out_file(filename.c_str(), ios::out);
vector<string>::const_iterator it = inp_vec.begin();
unsigned long long  counter=1;
while(it!= inp_vec.end())
{
 
out_file<<(*it);
if(!(counter%5))out_file<<'\n';
//
it++;
counter++;
}
}
void test_inp_file(string filename)
{
vector<string> inp_vec;
ifstream in_file(filename.c_str(), ios::in);
string str;
while(in_file>>str) inp_vec.push_back(str);
show_vec(inp_vec, filename);
}
void split(string str, vector<string> &arr,  string delim)//честно стащил из сетки (мог сам написать конечно, но и так хватило))
{
    arr.clear();
  size_t prev = 0;
  size_t next;
  size_t delta = delim.length();
 
  while( ( next = str.find( delim, prev ) ) != string::npos ){
    string tmp = str.substr( prev, next-prev );
    arr.push_back( str.substr( prev, next-prev ) );
    prev = next + delta;
  }
  string tmp = str.substr( prev ); 
  arr.push_back( str.substr( prev ) );
}
 
void make_res_file
(
 string filename, 
 string filename1, 
 string filename2,
 vector<pair<int, int>> &res_file_positions
 )
{
ofstream of_file(filename.c_str(), ios::out);
ifstream in_file1(filename1.c_str(), ios::in);
ifstream in_file2(filename2.c_str(), ios::in);
vector<pair<int, int>>::const_iterator it=res_file_positions.begin();
vector<string> strings;
int pos1(1), pos2(1);
string str_res, str1,str2;
for(;it!=res_file_positions.end(); it++)
{
int cnt(0);
pos2=1;
while(getline(in_file1, str1, '\n'))
{
if(pos1==it->first)
{
split(str1, strings, ";");
str1=strings[0]+";";
}
else
{
pos1++;
continue;
}
in_file2.seekg(0L);
pos2=1;
while(getline(in_file2, str2, '\n'))
{
if(pos2==it->second)
{
split(str2, strings, ";");
str2=strings[2];
pos2++;
pos1++;
goto hodu;
}
pos2++;
}//while
pos1++;
}//while
hodu:;//почему без кавычек не работает :D !!!
of_file<<str1<<str2<<endl;
}//for
}
 
void read_to_vec_pairs(string filename, vector<pair<int, pair<int, int>>> &inp_vec, bool first_unp_file=true)
{
inp_vec.clear();
vector<string> strings;
ifstream in_file(filename.c_str(), ios::in);
string str;
unsigned long counter=1;
int first,second;
while(getline(in_file, str, '\n'))
{
split(str, strings, ";");
if(first_unp_file)
{
first=atoi(strings[1].c_str());
second=atoi(strings[2].c_str());
inp_vec.push_back(make_pair(counter, make_pair(first,second)));
}
else
{
first=atoi(strings[0].c_str());
second=atoi(strings[1].c_str());
inp_vec.push_back(make_pair(counter, make_pair(first,second)));
}
counter++;
}
}
 
void first_inp_file_positions
(
vector<pair<int, pair<int, int>>>  &inp_vec_pairs1,
vector<pair<int, pair<int, int>>>  &inp_vec_pairs2,
vector<pair<int, int>> &res_file_positions
)
{
vector<pair<int, pair<int, int>>>::const_iterator 
it1=inp_vec_pairs1.begin(), it2;
while(it1!=inp_vec_pairs1.end())
{
it2=inp_vec_pairs2.begin();
while(it2!=inp_vec_pairs2.end())
{
if(it1->second.first==it2->second.first && it1->second.second==it2->second.second)
res_file_positions.push_back(make_pair(it1->first,it2->first));
it2++;
}
it1++;
}
}
 
 
 
 
int main(int argc, char* argv[])
{
SetConsoleCP (1251); SetConsoleOutputCP (1251);
string
filename1="filename1",
filename2="filename2",
str_arr1[]=
{
    "Андрей", ";",    "123",  ";",    "789",
    "Марина", ";",    "7250", ";",    "924",
    "Люба",     ";",    "7250", ";",    "924",
    "Светлана", ";",    "7251", ";",    "924",
    "Игорь",   ";",    "756758",";",   "7538"
},
str_arr2[]=
{
        "123",  ";",    "789",  ";", "AAA",
        "7250", ";",    "924",  ";", "CCC",
        "756758",";",   "7538"  ";", "IGP"
};
 
vector<string> 
inp_vec1(str_arr1, str_arr1+sizeof(str_arr1)/sizeof(str_arr1[0])),
inp_vec2(str_arr2, str_arr2+sizeof(str_arr2)/sizeof(str_arr2[0]));
 
save_inp_tofile(filename1,inp_vec1);
save_inp_tofile(filename2,inp_vec2);
test_inp_file(filename1);
test_inp_file(filename2);
cout<<endl;
vector<pair<int, pair<int, int>>>  inp_vec_pairs1,inp_vec_pairs2;
 
read_to_vec_pairs(filename1, inp_vec_pairs1);
cout<<endl;
read_to_vec_pairs(filename2, inp_vec_pairs2, false);
vector<pair<int, int>> res_file_positions;
first_inp_file_positions(inp_vec_pairs1, inp_vec_pairs2, res_file_positions);
show_vec(res_file_positions,"res_file_positions");
string filename3="resulting_file";
make_res_file(filename3,filename1,filename2,res_file_positions);
 
test_inp_file(filename3);
cout<<endl;
system("pause");
return 0;
}