int main () 
{
 
	ifstream inputFile ("C:/inputFile.txt");
	if ( !inputFile.is_open ())
	{
		cout<<"File not opened"<<endl;
	}
 
	string line;
	string userId, answers;
	while (std::getline (inputFile,line, '\n'))
	{
		std::stringstream inStream(line);
		inStream>>userId;
		std::getline(inStream, answers, '\n');
		cout<<"The userId is :"<<userId<<" and answers are: "<<answers<<endl;
 
	}
	inputFile.close ();
 
	return 0;
}

#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
 
using namespace std;
 
 
int getScore(string ans, string sol) {
	int score=0;
	for(int k=0; k<20; ++k) {
		if(ans[k]==sol[k])
			score+=2;
		else if(ans[k]==' ')
			score+=0;
		else
			--score;
	}
	return score;
}
 
char getGrade(int score) {
	double percent=(score/40.0)*100;
	if(percent>=90)
		return 'A';
	else if(percent>=80 && percent<89.99)
		return 'B';
	else if(percent>=70 && percent<79.99)
		return 'C';
	else if(percent>=60 && percent<69.99)
		return 'D';
	else
		return 'F';
}
 
void ID_ans (string combined, string &ID, string &answer)
{
	for (int counter=0;counter <9; counter++)
		ID[counter]= combined[counter];
	for (int counter=9; counter < 30; counter++)
		answer[counter] = combined[counter];	
}
int main()
{
	ifstream inputFile;
	ifstream ansFile;
	inputFile.open("Users/AlfB/Desktop/Student.txt");
	ansFile.open("Users/AlfB/Desktop/Answers.txt");
	string ans[20];
	string solutions;
	while(!ansFile.eof()) {
		ansFile >> solutions;
	}
	int k=0;
	cout << "STUDENT ID:\tANSWERS:\t\tSCORE:\tLETTER:" << endl;
	while(!inputFile.eof()) {
		string answers, line;
		string ID;
		while (std::getline (inputFile,line, '\n')){
		std::stringstream inStream(line);
		inStream>>ID;
		std::getline(inStream, answers, '\n');
		ID_ans(ID_ans,answers, solutions); // ERROR OCCURS HERE!!!!!!!!!! :(
		double score = getScore(answers, solutions);
		char letter = getGrade(score);
		cout << ID << "\t" << answers << "\t" << score << "\t" << letter << endl;
		ans[k]=answers;
		++k;
	}
	cout << endl;
 
	inputFile.close();
	ansFile.close();
	return 0;
}

char CalculateGrade (const double percent)
{
 
	if (percent >= 90)
		return 'A';
	else if (percent >= 80)
		return 'B';
	else if (percent >= 70)
		return 'C';
	else if (percent >= 60)
		return 'D';
	else if (percent >= 50)
		return 'E';
	else 
		return 'F';
}
 
double CalculateAnswers (const string& studentsResponse, const string& answers)
{
	double  score = 0;
 
	for (size_t i=0; i< answers.length (); ++i)
	{
		if (studentsResponse[i] == answers[i])
		{
			++score;
		}
		else
		{
			--score;
		}
	}
 
	double percent = (score/answers.length ())*100;
	return percent;
}
 
int main () 
{
 
	ifstream inputFile ("C:/inputFile.txt");
	ifstream answersFile ("C:/answers.txt");
 
	if ( !inputFile.is_open ())
	{
		cout<<"File not opened"<<endl;
	}
 
	if (!answersFile.is_open ())
	{
		cout<<"Answers File not Opened"<<endl;
	}
 
 
 
	string answer;				//read from file...
	// Reading the answer from answers File.
	std::getline (answersFile, answer, '\n');
	answersFile.close ();
	answersFile.clear ();
 
	// Reading the Input File...
	string line;
	string userId, studentResponse;
	while (std::getline (inputFile,line, '\n'))
	{
		// you have student's answer in variable -->studentResponse, and id --> userId.
		std::stringstream inStream(line);
		inStream>>userId;
		inStream.get();
		std::getline(inStream, studentResponse, '\n');
 
		//Compare the answers.
		double score = CalculateAnswers (studentResponse, answer);
 
		// Calculate the Grade.
		char grade = CalculateGrade (score);
 
		cout<<"The Student :"<<userId<<" got "<<grade<<" grade"<<endl;
 
	}
 
	inputFile.close ();
 
	return 0;
}