Написать библиотеку функций для работы с однонаправленным линейным списком

#include <iostream>
#include <fstream> 
#include <math.h> 
#include <stdlib.h> 
#include <string.h> 
using namespace std;
 
struct cities{
    char name[25];
    float price;
    char firma[20];
    int amount;
    char sort[20];
    cities *first;
};
 ifstream f_in;
 ofstream fout;
cities *first1=NULL;
cities *first2=NULL;
int filein1(){
    cities *tmp;
    if (first1==NULL){
        
        tmp=new cities;
        f_in >> tmp->name >> tmp->firma >> tmp->sort >> tmp->price >> tmp->amount;
        tmp->first==NULL;
     
        first1=tmp;
    
        }   
    else {
        tmp=first1;
        while (tmp->first!=NULL){
            tmp=tmp->first;}
        cities *tmp2=new cities;
        f_in >> tmp2->name >> tmp2->firma >> tmp2->sort >> tmp2->price >> tmp2->amount;
        tmp->first=tmp2;
        tmp2->first=NULL;
    }
}
int filein2(){
    cities *tmp;
    if (first2==NULL){
        
        tmp=new cities;
        f_in >> tmp->name >> tmp->firma >> tmp->sort >> tmp->price >> tmp->amount;
        tmp->first==NULL;  
        first2=tmp;
    
        }   
    else {
        tmp=first2;
        while (tmp->first!=NULL){
            tmp=tmp->first;}
        cities *tmp2=new cities;
        f_in >> tmp2->name >> tmp2->firma >> tmp2->sort>> tmp2->price >> tmp2->amount;
        tmp->first=tmp2;
        tmp2->first=NULL;
    }
}
 
 
int out1(){
    if (first1!=NULL){
    cities *tmp;
    tmp=first1;
    while (tmp->first!=NULL)    {
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
        tmp=tmp->first;
    }
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
    }
}
 
int out2(){
    if (first2!=NULL){
    cities *tmp;
    tmp=first2;
    while (tmp->first!=NULL)    {
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
        tmp=tmp->first;
    }
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
    }
}
 
 
int add1(){
    cities *tmp;
    if (first1==NULL){
        
        tmp=new cities;
        cin >> tmp->name >> tmp->firma >> tmp->sort >> tmp->price >> tmp->amount;
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
        tmp->first==NULL;  
        first1=tmp;
    
        }   
    else {
        tmp=first1;
        while (tmp->first!=NULL){
            tmp=tmp->first;}
        cities *tmp2=new cities;
        cin >> tmp2->name >> tmp2->firma >> tmp2->sort >> tmp2->price >> tmp2->amount;
        cout << tmp2->name  << " " << tmp2->firma << " " << tmp2->sort << " "<< tmp2->price << " "<< tmp2->amount << endl;
        tmp->first=tmp2;
        tmp2->first=NULL;
    }
}
 
int add2(){
    cities *tmp;
    if (first2==NULL){
        
        tmp=new cities;
        cin >> tmp->name >> tmp->firma >> tmp->sort >> tmp->price >> tmp->amount;
        cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
        tmp->first==NULL;  
        first2=tmp;
    
        }   
    else {
        tmp=first2;
        while (tmp->first!=NULL){
            tmp=tmp->first;}
        cities *tmp2=new cities;
        cin >> tmp2->name >> tmp2->firma >> tmp2->sort >> tmp2->price >> tmp2->amount;
        cout << tmp2->name  << " " << tmp2->firma << " " << tmp2->sort << " "<< tmp2->price << " "<< tmp2->amount << endl;
        tmp->first=tmp2;
        tmp2->first=NULL;
    }
}
 
 
int source1(){
    char sourcing[25];
    cout << "name: ";
    cin >> sourcing;
        cities *tmp;
        int k=0;
    if (first1==NULL){cout << endl << "You dont enter your list.";}
    else {
        tmp=first1;
        while (tmp->first!=NULL){
            if (strcmp(tmp->name, sourcing)==0){
            cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
                k=1;
            }
            tmp=tmp->first;}
            if (strcmp(tmp->name, sourcing)==0){
                cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
                k=1;
            }
            
    }
     if (k==0){
        cout << "Program cannot find this value." << endl;
    }
    
}
 
int source2(){
    char sourcing[25];
    cout << "name: ";
    cin >> sourcing;
        cities *tmp;
        int k=0;
    if (first2==NULL){cout << endl << "You dont enter your list.";}
    else {
        tmp=first2;
        while (tmp->first!=NULL){
            if (strcmp(tmp->name, sourcing)==0){
                cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
                k=1;
            }
            tmp=tmp->first;}
            if (strcmp(tmp->name, sourcing)==0){
                cout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
                k=1;
            }
            
    }
     if (k==0){
        cout << "Program cannot find this value." << endl;
    }
}
 
 
int del1(){
    char deleting[25];
    cout << "name for delete";
    cin >> deleting;
    int k=0;
 cities **tmp=&first1;
    while (*tmp)
    {
        cities *tmp1=*tmp;
        if (strcmp(tmp1->name, deleting)==0)
        {
            *tmp = tmp1->first;
            delete tmp1;
            k=1;
        }
        else
            tmp = &tmp1->first;
    }
    if (k==0){
        cout << "Program cannot find this value." << endl;
    }
}
 
int del2(){
    char deleting[25];
    cout << "name for delete: ";
    cin >> deleting;
    int k=0;
 cities **tmp=&first2;
    while (*tmp)
    {
        cities *tmp1=*tmp;
        if (strcmp(tmp1->name, deleting)==0)
        {
            *tmp = tmp1->first;
            delete tmp1;
            k=1;
        }
        else
            tmp = &tmp1->first;
    }
    if (k==0){
        cout << "Program cannot find this value." << endl;
    }
}
 
 
int fileout1(){
    if (first1!=NULL){
    cities *tmp;
    tmp=first1;
    while (tmp->first!=NULL)
    {
        fout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
        tmp=tmp->first;
    }
        fout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
    }
}
 
int fileout2(){
    if (first2!=NULL){
    cities *tmp;
    tmp=first2;
    while (tmp->first!=NULL)    {
    fout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;       tmp=tmp->first;
    }
        fout << tmp->name  << " " << tmp->firma << " " << tmp->sort << " "<< tmp->price << " "<< tmp->amount << endl;
    }
}
 
 
int comparison(){
    int k, l=1, g=1;
    k=1;
    cities *tmp1, *tmp2;
    tmp1=first1;
    tmp2=first2;
    while (tmp1->first!=NULL){
        l++;
        tmp1=tmp1->first;
    }
    while (tmp2->first!=NULL){
        g++;
        tmp2=tmp2->first;
    }
    tmp1=first1;
    tmp2=first2;
    if (l!=g){ k=0; cout << k;}
    else {
        for (int i=0; i<l; i++){
            if ((strcmp(tmp1->name, tmp2->name)!=0)||(tmp1->firma!=tmp2->firma)||(tmp1->sort!=tmp2->sort)||(tmp1->price!=tmp2->price)||(tmp1->amount!=tmp2->amount)){k=0;
            }
            tmp1=tmp1->first;
            tmp2=tmp2->first;
        }   
    }
    if (k==0){  cout << "This lists are not identical." << endl;
    }
    else { cout << "This lists are identical.";
    }
 
}
 
int main(void) {
    int a, b, c;
    cout << "Please, press 1 if you want to work with first list or press 2 if you want to work with second list. If you want to comparise your lists, press 3. If you want to close program, press 0.";
    cin >> a;
    cout << endl;
    while (a!=0){
        while (a==1){
            cout << " key:" << endl << "1 - filein;" << endl << "2 - out;" << endl << "3 - add;" << endl << "4 - source;" << endl << "5 - delete;" << "6 - fileout. ";
            cin >> b;
            cout << endl;
            switch (b) {
            case 1: {   f_in.open("L1.txt",ios::in);
                while (!f_in.eof()) {filein1();}
                out1();
                f_in.close();
                break;
            };
            case 2: out1(); break;
            case 3: add1(); break;
            case 4: source1(); break;
            case 5: del1(); break;
            case 6: {fout.open("L3new.txt",ios::app); fileout1();fileout2(); fout.close();
                break;
            }; 
             }
        cout << "Please, press 1 if you want to work with first list or press 2 if you want to work with second list. If you want to comparise your lists, press 3. If you want to close program, press 0.";
        cin >> a;
        cout << endl;
        }
        while (a==2){
            cout << "Please, choose one of this function and press key:" << endl << "1 - filein;" << endl << "2 - out;" << endl << "3 - add;" << endl << "4 - source;" << endl << "5 - delete;" << "6 - fileout. ";
            cin >> b;
            cout << endl;
            switch (b) {
            case 1: {   f_in.open("L2.txt",ios::in);
                while (!f_in.eof()) {filein2();}
                out2();
                f_in.close();
                break;
            };
            case 2: out2(); break;
            case 3: add2(); break;
            case 4: source2(); break;
            case 5: del2(); break;
            case 6: {fout.open("L2new.txt",ios::app); fileout2(); fout.close();
                break;
            }; 
             }
        cout << "Please, press 1 if you want to work with first list or press 2 if you want to work with second list. If you want to comparise your lists, press 3. If you want to close program, press 0.";
        cin >> a;
        cout << endl;
        }
        while (a==3){
            comparison();
            cout << "Please, press 1 if you want to work with first list or press 2 if you want to work with second list. If you want to comparise your lists, press 3. If you want to close program, press 0.";
            cin >> a;
            cout << endl;
        }
    }
    
    return 0;
}