Singly-linked list v0.3 - Data structures, exercise

#include <iostream>
#include <vector>
#include <string>
#include <fstream>
using namespace std;

struct _student {
    string frist_name;
    string last_name;
    int grade;
    _student *pNextStudent;
};

void InsertAfter (_student *head);
void PrintAll (_student *head);
void InsertBefore (_student *head);
void FindElement (_student *head);
void DeleteElement (_student *head);
void WriteDB_toFile (_student *head, fstream *database, string FileName);
void RebuildDB_fromFile (_student *head, fstream *database, string FileName);

int main ()
{
    _student *head = new _student;
    head->pNextStudent=NULL;
    int N=0, i=0, selection=0;
    fstream database;
    string FileName = "database.txt";

    while (selection != 8){
        cout << "* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ";
        cout << "\nWhat do you wish to do today my lord?" << endl << endl;
        cout << "I want to:\n\n1) Add new students to existing database.\n2) I wish to print all current students from database.";
        cout << "\n3) I wish to Insert new student at specific place.\n4) I want to check if student exists in database.\n5) I want to delete student from database.";
        cout << "\n6) I want to write database to file.\n7) I want to rebuild database from file.\n8) exit" << endl;
        cin >> selection;

        switch(selection){
        case 1:
            cout << "\nHow many students do you wish to append? ";
            cin >> N;
            i = 0;
            do{
                InsertAfter(head);
                i++;
            }while(i<N);
            break;

        case 2:
            PrintAll(head);
            break;

        case 3:
            InsertBefore(head);
            break;

        case 4:
            FindElement(head);
            break;

        case 5:
            DeleteElement(head);
            break;

        case 6:
            WriteDB_toFile(head,&database,FileName);
            break;

        case 7:
            RebuildDB_fromFile(head,&database,FileName);
            break;

        case 8:
            exit(0);
            break;

        default:
            cout << "Wrong selection. Please try again!" << endl;
            break;
        }
    }

    getchar();
    return 0;
}

bool isNumber(string line) {
    return (atoi(line.c_str()));
}

void InsertAfter(_student *head){
    _student *counter=head;

    while(counter->pNextStudent!=NULL)
        counter=counter->pNextStudent;

    _student *newStudent = new _student;
    newStudent->pNextStudent=NULL;
    counter->pNextStudent=newStudent;

    cout << "\nType students first name: ";
    cin >> newStudent->frist_name;

    cout << "Type students last name: ";
    cin >> newStudent->last_name;

    cout << "Type students " << newStudent->frist_name << " " << newStudent->last_name << " grade: ";
    cin >> newStudent->grade;
}

void PrintAll (_student *head){
    _student * counter;
    counter=head->pNextStudent;
    while(counter!=NULL){
        cout << "\nStudents first name: " << counter->frist_name << endl << "Students last name: " << counter->last_name << endl;
        cout << "Students grade: " << counter->grade << endl;
        counter=counter->pNextStudent;
    };
}

void InsertBefore(_student *head)
{
    _student *counter = head->pNextStudent;

    string first_name,last_name;
    cout << "\nEnter the first and last name of student, before you wish to add new student: ";
    cin >> first_name >> last_name;

    while (counter!=NULL)
    {
        if ((counter->pNextStudent->frist_name==first_name)&&(counter->pNextStudent->last_name==last_name))
        {
            _student * newStudent = new _student;

            cout << "\nType students first name: ";
            cin >> newStudent->frist_name;

            cout << "Type students last name: ";
            cin >> newStudent->last_name;

            cout << "Type students " << newStudent->frist_name << " " << newStudent->last_name << " grade: ";
            cin >> newStudent->grade;


            newStudent->pNextStudent=counter->pNextStudent;
            counter->pNextStudent=newStudent;
            break;
        }
        else if (counter->pNextStudent==NULL)
            cout << "Student not found!\nPlease try again" << endl;

        else
            counter=counter->pNextStudent;
    }
}

void FindElement (_student *head){
    _student *counter = head;
    string filter;
    vector <_student*> addresses;

    cout << "\nType students first name, last name or grade to list all students with selected filter:" << endl;
    cin >> filter;

    if(isNumber(filter))
        while(counter!=NULL){
            if (counter->grade==atoi(filter.c_str()))
                addresses.push_back(counter);
            counter=counter->pNextStudent;
        }
    else
        while (counter!=NULL){
            if((counter->frist_name==filter)||(counter->last_name==filter))
                addresses.push_back(counter);
            counter=counter->pNextStudent;
        }

        if(addresses.size()!=NULL)
        {
            cout << "\nFollowing students were found using filter: " << filter << endl << endl;
            for (int i=0; i<addresses.size(); i++)
            {
                cout << "Students first name: " << addresses[i]->frist_name << endl;
                cout << "Students last name: " << addresses[i]->last_name << endl;
                cout << "Students grade: " << addresses[i]->grade << endl << endl;
            }
        }
        else
            cout << "\nNo students were found in database using following filter: " << filter << endl << endl;
}

void DeleteElement (_student *head){
    _student * counter = head;
    string first_name, last_name;

    cout << "Enter the first and last name of student you wish to remove from database: ";
    cin >> first_name >> last_name;

    while(counter->pNextStudent!=NULL)
    {
        if((first_name==counter->pNextStudent->frist_name)&&(last_name==counter->pNextStudent->last_name))
        {
            _student * toRemove = counter->pNextStudent;
            counter->pNextStudent=counter->pNextStudent->pNextStudent;
            delete toRemove;
        }
        if (counter->pNextStudent!=NULL)
            counter=counter->pNextStudent;
    }
}

void WriteDB_toFile (_student *head, fstream *database,string FileName){
    _student *current = head->pNextStudent;
    //remove(FileName);
    (*database).open(FileName.c_str());

    (*database) << "* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *" << endl;
    (*database) << "*\t\tFirst name\t\t|\t\tLast name\t\t|\t\tGrade\t\t*" << endl;
    (*database) << "* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *" << endl;
    while (current!=NULL)
    {
        if (current->frist_name.size() <= 3)
            (*database) << "*\t" << current->frist_name << "\t\t\t\t\t|\t";
        else if (current->frist_name.size() <= 7)
            (*database) << "*\t" << current->frist_name << "\t\t\t\t|\t";
        else if (current->frist_name.size() >= 12)
            (*database) << "*\t" << current->frist_name << "\t\t|\t";
        else
            (*database) << "*\t" << current->frist_name << "\t\t\t|\t";

        if (current->last_name.size() <= 3)
            (*database) << current->last_name << "\t\t\t\t\t|\t\t";
        else if (current->last_name.size() <= 7)
            (*database) << current->last_name << "\t\t\t\t|\t\t";
        else if (current->last_name.size() >= 12)
            (*database) << current->last_name << "\t\t|\t\t";
        else
            (*database) << current->last_name << "\t\t\t|\t\t";

        if (current->grade < 1000)
            (*database) << current->grade << "\t\t\t*" << endl;
        else if (current->grade > 9999999)
            (*database) << current->grade << "\t*" << endl;
        else
            (*database) << current->grade << "\t\t*" << endl;
        current=current->pNextStudent;
    }
    (*database) << "* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *";
    (*database).close();
}

void RebuildDB_fromFile (_student *head, fstream *database, string FileName){
    _student *counter=head;
    (*database).open(FileName.c_str());
    string temp;
    string clean;

    getline((*database),temp,'\n');
    getline((*database),temp,'\n');
    getline((*database),temp,'\n');

    while ((*database).good())
    {
        _student *newStudent = new _student;

        while (counter->pNextStudent!=NULL)
            counter = counter->pNextStudent;

        getline((*database),temp,'|');
        for (int i=0; i<temp.size(); i++)
        {
            if ((temp[i]!='\t') && (temp[i]!='*'))
                clean.push_back(temp[i]);
        }
        newStudent->frist_name=clean;
        clean.clear();

        getline((*database),temp,'|');
        for (int i=0; i<temp.size(); i++)
        {
            if ((temp[i]!='\t') && (temp[i]!='*'))
                clean.push_back(temp[i]);
        }
        newStudent->last_name=clean;
        clean.clear();

        getline((*database),temp,'\n');
        for (int i=0; i<temp.size(); i++)
        {
            if ((temp[i]!='\t') && (temp[i]!='*'))
                clean.push_back(temp[i]);
        }
        newStudent->grade=atoi(clean.c_str());
        clean.clear();

        counter->pNextStudent=newStudent;
        newStudent->pNextStudent=NULL;
    }
    counter=head;
    while(counter->pNextStudent->pNextStudent!=NULL)
    {
        counter=counter->pNextStudent;
    }
    _student * toRemove = counter->pNextStudent;
    delete toRemove;
    counter->pNextStudent=NULL;
    (*database).close();
}