Need help with int[int] array subscript error

[CatcherOne]

Creating a program to have the user make their own exam. In the part where i am suppose to ask the user how many questions they would like their exam to be, i am having trouble with. Spent a few hours trying to figure why i am having the int[int] array subscript error. Need a hint into the right direction with this. Error is on line 240/248.

#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>

using namespace std;

/* Class files for the Question Classes.  Designed so that the base class could be used as the collection class later in the program.  Base Question Class has several methods that are identified as virtual as they will be redefined later in the hierarchy to specify the types of questions that will be read from or written to files */

class Question // super class
{
public:

	string getQuestion()//gets the question
	{
		return question;
	}
	virtual int getValue() //gets the point value of the question
	{
	return value;
	}
	virtual string getQuestionType()// gets the type of question
	{
		return questiontype;
	}
	virtual void setQuestion(string answer, int value)
	{
	}
	virtual void setNewQuestion(string answer, int value)
	{
	}
	virtual void printOptions()
	{
	}

	virtual string getAnswer()
	{
		return answer;
	}

private:
	string question,  answer;
    int value;
    string questiontype;
};


//The class for True/False Questions
class QuestionTF: public Question// class for true and false questions
{
public:
	void setQuestion(string theQuestion, int pointValue)
	{
		string theAnswer;
		questiontype = "TF";
		question = theQuestion;
		value = pointValue;
		options = "true/false";
		//get the answer from the file
		getline(cin,theAnswer);
		answer = theAnswer;
	}

	void setNewQuestion(string theQuestion, int pointValue)
	{
		string theAnswer;
		questiontype = "TF";
		question = theQuestion;
		value = pointValue;
		options = "true/false";
		//get the answer from user
		cout<<"Enter answer true/false\n";
		getline(cin,theAnswer);
		answer = theAnswer;
	}

	int getValue() //gets the point value of the question
	{
		return value;
	}

	string getQuestionType()// gets the type of question
	{
		return questiontype;
	}

	void printOptions()//prints the options for that question
	{
		cout<<question<<endl;
		cout<<answer<<endl;
	}

	string getAnswer()//outputs the answer for that question
	{
		return answer;
	}
private:
	string question, questiontype;
	string answer;
	string options;
	int value;
};
//The class for Multiple Choice Questions

class QuestionMC: public Question//class for multiple choice
{
public:
	void setQuestion(string theQuestion, int pointValue)
	{
		string line;
		questiontype = "MC";
		//get the number of choices from the file
		getline(cin,line);
		numberOfOptions = atoi(line.c_str());
		question = theQuestion;
		value = pointValue;
		//get the individual choice lines and load to options array
		for (int count = 0; count<numberOfOptions;count++){
			getline(cin,line);
			options[count] = line;
		}
		//get the answer from the file and load into answer
		getline(cin, line);
		answer = line;
	}

	void setNewQuestion(string theQuestion, int pointValue)
	{
		string line;
		questiontype = "MC";
		//get the number of choices from the user
		cout<<"Enter the number of choices:  ";
		getline(cin,line);
		numberOfOptions = atoi(line.c_str());
		question = theQuestion;
		value = pointValue;
		//get the individual choice lines and load to options array
		for (int count = 0; count<numberOfOptions;count++){
		    cout<<"\nEnter next option:  ";
			getline(cin,line);
			options[count] = line;
		}
		//get the answer from the user and load into answer
		cout<<"\nEnter Answer:  ";
		getline(cin, line);
		answer = line;
	}
	void printOptions()// prints the questions, options, and answer
	{
		char first = 'A';
		cout<<question<<endl;
		for(int count = 0; count<numberOfOptions;count++){
			cout<<first++ <<".  "<<options[count]<<"\n";
		}
		cout<< answer << "\n";
	}

	int getValue() //gets the point value of the question
	{
		return value;
	}

	string getQuestionType()// gets the type of question
	{
		return questiontype;
	}

	string getAnswer()// prints the answer
	{
		return answer;
	}
private:
	int numberOfOptions;
	string question, answer;
	string options[6];
	string questiontype;
	int value;
};


//  Function prototypes for the functions supporting the main program functionality

int  loadArray(Question *myQuestions[]);
int addQuestion(Question *myQuestions[], int numquestions);
void printQuizQuestions(Question *myQuestions[], int numquestions);
void writeExamQuestionFile(Question *myQuestions[], int numquestions);


// Function to load the array of Questions from the input file
int loadArray(Question *myQuestions[])
{
string line;
string questiontype, theQuestion;
int numquestions, questionvalue;

//get the number of questions from the first line in the file
	getline(cin,line);
	numquestions = atoi(line.c_str());
	for(int count = 0; count<numquestions;count++){
		getline(cin,line);
		//get the next line with the question type and the value of the question
		int npos = line.size();
		int prev_pos = 0;
		int pos = 0;
		while( line[pos]!=' ')
			pos++;
		questiontype = line.substr(prev_pos, pos-prev_pos);
		prev_pos = ++pos;
        questionvalue = atoi(line.substr(prev_pos, npos-prev_pos).c_str()); // Last word

	   //process a true/false question
		if (questiontype == "TF")
		{
			myQuestions[count] = new QuestionTF;
			getline(cin,theQuestion);
			myQuestions[count]->setQuestion(theQuestion,questionvalue);
		}
		//process a multiple choice question
		if (questiontype =="MC")
		{
			myQuestions[count] =new QuestionMC;
			getline(cin,theQuestion);
			myQuestions[count]->setQuestion(theQuestion,questionvalue);
		}

	}
	return numquestions;
}


//Function to add questions by getting from user and using he interactive methods //added to the classes.
int addQuestion(Question *myQuestions[], int numquestions)
{
        int questionvalue;
        int count = numquestions;
        string theQuestion,line, questiontype;
        //Asking user how many questions user wants to create
        //create loop
        for (int count = 0; count<numquestions;count++){
        	if (numquestions== 0){
			cout<<"Enter the amount of questions for the exam\n";
        		getline(cin,line);
        		numquestions = atoi(line.c_str());
        		numquestions[count] = line;        	
		} else
		{
			cout<<"Enter the amount of questions for the exam\n";
        		getline(cin,line);
        		numquestions = atoi(line.c_str());
        		numquestions[count] = line;
		}
}
        cout<<"Enter the Question type and value\n";
        getline(cin,line);
		//get the next line with the question type and the value of the question
		int npos = line.size();
		int prev_pos = 0;
		int pos = 0;
		while( line[pos]!=' ')
			pos++;
		questiontype = line.substr(prev_pos, pos-prev_pos);
		prev_pos = ++pos;
        questionvalue = atoi(line.substr(prev_pos, npos-prev_pos).c_str()); // Last word

	   //process a true/false question
		if (questiontype == "TF")
		{
			myQuestions[count] = new QuestionTF;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		//process a multiple choice question
		if (questiontype =="MC")
		{
			myQuestions[count] =new QuestionMC;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		return ++numquestions;
}



// Function to print out the Quiz questions from the Array. Uses methods from the
// classes developed to allow this printing to be done generically to screen or file.
void printQuizQuestions(Question *myQuestions[], int numquestions)
{
//print out the questions that have been processed
	for(int count = 0; count<numquestions;count++)
	{
		myQuestions[count]->printOptions();
		cout<<"\n";
	}
}

[TheIdeasMan]

Hi,

Can you tell us what the type of the numquestions variable is? You should then see why trying to use it as an array won't work.

Consider using std::vector instead of arrays, they were invented to avoid the problems that arrays have.

Edit:

What is the go with line 257? That is not the purpose of npos.

https://en.cppreference.com/w/cpp/string/basic_string/npos

Also, IMO your functions are too long, your comments actually give good clues how to split the code into functions.

[CatcherOne]

Hello TheIdeasMan,

So I've been working on the code. I've done some changes to it and it compiles good but it wont ask the user for another question. The program ends after only asking once.
From this:

//Function to add questions by getting from user and using he interactive methods //added to the classes.
int addQuestion(Question *myQuestions[], int numquestions)
{
        int questionvalue;
        int count = numquestions;
        string theQuestion,line, questiontype;
        //Asking user how many questions user wants to create
        //create loop
        for (int count = 0; count<numquestions;count++){
        	if (numquestions== 0){
			cout<<"Enter the amount of questions for the exam\n";
        		getline(cin,line);
        		numquestions = atoi(line.c_str());
        		numquestions[count] = line;        	
		} else
		{
			cout<<"Enter the amount of questions for the exam\n";
        		getline(cin,line);
        		numquestions = atoi(line.c_str());
        		numquestions[count] = line;
		}
}
        cout<<"Enter the Question type and value\n";
        getline(cin,line);
		//get the next line with the question type and the value of the question
		int npos = line.size();
		int prev_pos = 0;
		int pos = 0;
		while( line[pos]!=' ')
			pos++;
		questiontype = line.substr(prev_pos, pos-prev_pos);
		prev_pos = ++pos;
        questionvalue = atoi(line.substr(prev_pos, npos-prev_pos).c_str()); // Last word

	   //process a true/false question
		if (questiontype == "TF")
		{
			myQuestions[count] = new QuestionTF;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		//process a multiple choice question
		if (questiontype =="MC")
		{
			myQuestions[count] =new QuestionMC;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		return ++numquestions;
}

To this:

//Function to add questions by getting from user and using he interactive methods //added to the classes.
int addQuestion(Question *myQuestions[], int numquestions)
{
        int questionvalue;
        int count=numquestions;
        string questions[numquestions];
        string theQuestion,line, questiontype;
        //Asking user how many questions he wants to create
        cout<<"Enter the amount of questions for the exam\n";
        getline(cin,line);
        for (int count = 0; count<numquestions;count++){
        	getline(cin,line);
        	questions[count] = line;
}

        cout<<"Enter the Question type and value\n";
        getline(cin,line);
		//get the next line with the question type and the value of the question
		int npos = line.size();
		int prev_pos = 0;
		int pos = 0;
		while( line[pos]!=' ')
			pos++;
		questiontype = line.substr(prev_pos, pos-prev_pos);
		prev_pos = ++pos;
        questionvalue = atoi(line.substr(prev_pos, npos-prev_pos).c_str()); // Last word

	   //process a true/false question
		if (questiontype == "TF")
		{
			myQuestions[count] = new QuestionTF;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		//process a multiple choice question
		if (questiontype =="MC")
		{
			myQuestions[count] =new QuestionMC;
			cout<<" \nEnter the Question: ";
			getline(cin,theQuestion);
			myQuestions[count]->setNewQuestion(theQuestion,questionvalue);
		}
		return ++numquestions;
}

[TheIdeasMan]

Hi,

I think you still have a problem with variable length arrays (it should not compile), best thing to do is use a std::vector like I mentioned before. It's a VLA because numquestions is a variable. The size of an array needs to be known at compile time, so use a std::vector.

Don't use new, it's problematic, use std::vector instead.

With the amount of code in a function, a function should do one conceptual thing only, try to keep the code to 30 lines or less. Shorter functions aid readability and understanding.