What am I doing wrong???

[N1ghtm4r3]

This code compiles but it crashes after inputting answers for the students questions. It will output the first "[studName] has the following questions correct: " and then crashes before outputting anything.

It uses multidimensional vectors which I guess I'm having a bit of trouble understanding. I take it I'm populating the vector incorrectly, or missing something.

Please help, Ive been stuck on this for days.

PS - Lots of unnecessary commenting for school

#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>

using namespace std; //STD library

int main()
{
	vector<string> studName;         //
	vector<char> corrAns;            //
	vector<char> studAns;            //
	vector<int> numCorr;             //
	char correctAns;                 //Fairly
	char studentAns;                 //Self
	string nameStud;                 //Explanitory
	int numStud = 0;                 //
	int questions = 0;               //

	cout << "How many questions will be asked?" << endl; //How many questions to score
	cin >> questions;   //cin num of questions
	numCorr.resize(questions);


	for(int x=0; x<questions; x++) {  //FOR loop to populate correct answers in vector
		cout << "Enter the answer for question " << x+1 << "[A,B,C,D]: " << endl; //cout question
		cin >> correctAns;  //cin answer
		corrAns.push_back(correctAns);  //pushing each answer into vector
	}

	cout << "Enter the number of students to test: " << endl; //asking for number of students to test
	cin >> numStud;  //cin num of students

	


	vector< vector<char> > studentAnswers(numStud, vector<char>(questions)); //Multi-dimensional vector to keep track of students, answers, percentage.

	for(int i=0; i<numStud; i++) {    //FOR loop to populate names of students being tested
		cout << "Enter the name of student " << i + 1 << ": " << endl;  //cout question
		cin >> nameStud;   //cin name of students
		studName.push_back(nameStud);  //push back each name into vector
		vector<char> row;  //
		
		for(int j=0; j<questions; j++) {   //FOR loop to populate each students answers
			cout << "Enter the answer for question " << j+1 << ": " << endl;  //cout question
			cin >> studentAns;   //cin answer
			studentAnswers.push_back(studAns);  // 
		}

		studentAnswers[i] = row;  //
		row.clear();  //call in destructors
	}

	for(int k=0; k<numStud; k++) {  //FOR loop for students correct answers
	
		cout << studName[k] << " was correct on the following questions: "; //cout correct?

		for(int l=0; l<questions; l++){  //FOR loop to compare and output ans
			if (studentAnswers[k][l] == corrAns[l]) { //compare
				cout << l << " ";  //cout questions correct
				numCorr.push_back(k);  //counter
			}
		cout << endl;  //spacer
		cout << "for a total of " << numCorr[k] << " answers." << endl; //total correct answers
		cout << "And a percentage of " << ((numCorr[k]/questions) * 100) << "%." << endl << endl;  //percentage correct

		}


	}

	system("pause"); //system pause
	return 0; //return
}

Thanks for any help everyone!!!

[hamsterman]

Line 51 sets studentAnswers[i] to row which is empty, so trying to access some element of it causes an error. Why do you think that you need that row vector at all?

[N1ghtm4r3]

I guess I might not, to be honest, I let a friend revise the code, because he thought itd be cool to introduce me to multidimensional arrays. Now, I'm stuck with this by myself trying to debug it and I dont have time to revise it to how I had it.

Thanks for the suggestion. Do you have anymore I could apply to fix this mess?

**EDIT**

Alright, so I got rid of the multidimensional vector, just too many headaches for a beginner like me. Now I think I', back on the right track. How does this look?

#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>

using namespace std; //STD library

int main()
{
	vector<string> studName;         //
	vector<char> corrAns;            //
	vector<char> studAns;            //
	vector<int> numCorr;             //
	char correctAns;                 //Fairly
	char studentAns;                 //Self
	string nameStud;                 //Explanitory
	int numStud = 0;                 //
	int questions = 0;               //

	cout << "How many questions will be asked?" << endl; //How many questions to score
	cin >> questions;   //cin num of questions

	for(int x=0; x<questions; x++) {  //FOR loop to populate correct answers in vector
		cout << "Enter the answer for question " << x+1 << "[A,B,C,D]: " << endl; //cout question
		cin >> correctAns;  //cin answer
		corrAns.push_back(correctAns);  //pushing each answer into vector
	}

	cout << "Enter the number of students to test: " << endl; //asking for number of students to test
	cin >> numStud;  //cin num of students

	for(int i=0; i<numStud; i++) {    //FOR loop to populate names of students being tested
		cout << "Enter the name of student " << i + 1 << ": " << endl;  //cout question
		cin >> nameStud;   //cin name of students
		studName.push_back(nameStud);  //push back each name into vector
		 
		
		for(int j=0; j<questions; j++) {   //FOR loop to populate each students answers
			cout << "Enter the answer for question " << j+1 << ": " << endl;  //cout question
			cin >> studentAns;   //cin answer
			studAns.push_back(studentAns);  // 
		}

		 
	}

	for(int k=0; k<numStud; k++) {  //FOR loop for students correct answers
	
		cout << studName[k] << " was correct on the following questions: "; //cout correct?

		for(int l=0; l<questions; l++){  //FOR loop to compare and output ans
			if (studAns[l] == corrAns[l]) { //compare
				cout << l << " ";  //cout questions correct
				numCorr.push_back(k);  //counter
			}
		}
		cout << endl;  //spacer
		cout << "for a total of " << numCorr[k] << " answers." << endl; //total correct answers
		cout << "And a percentage of " << ((numCorr[k]/questions) * 100) << "%." << endl << endl;  //percentage correct

	}

	system("pause"); //system pause
	return 0; //return
}

It compiles, but not working quite properly. Any suggestions are appreciated.

[N1ghtm4r3]

Bump

[N1ghtm4r3]

Bump please???

[hamsterman]

Have patience..

The problem with the numCorr. For every correct answer, you push the id of the student into a vector and later you take the kth value of the vector full of k (this could break, if numStud > questions, by the way). How does that make sense? What you should be doing is incrementing some integer and printing it..

Also, the % thing will always be 0 or 100 because due to integer division 2/3=0. You can do multiplication before division to avoid this tough.