bubble sort crashing program c++ - c++

Question

So I've been working on a project for class and everything was going swimmingly, until I had to sort the information by last name in ascending order. To elaborate further, in my program I am supposed to take file input, apply it into whatever kind of variables I see fit, calculate their grades by comparing their answers against an answer key, and then sort the entries by last name. Without further ado here is my code! (be gentle)
#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <algorithm>
const int TEST_SIZE = 10;
using namespace std;
struct StudentInfo
{
int id;
string fName;
string lName;
char testAnswers[10];
int totalPoints = 0;
int avg = 0;
char letterGrade;
};
void inputInfo(char[], StudentInfo[]);
void calcGrade(char[], StudentInfo[]);
void bubbleSort(StudentInfo[]);
void outputInfo(StudentInfo[]);
int main()
{
StudentInfo studentInfo[10];
string temp;
char answerKey[10];
inputInfo(answerKey, studentInfo);
calcGrade(answerKey, studentInfo);
bubbleSort(studentInfo);
outputInfo(studentInfo);
return 0;
}
void inputInfo(char answerKey[], StudentInfo studentInfo[])
{
cout << "Please enter the 10-question answer key: \n";
for(int i = 0; i < TEST_SIZE; i++)
{
cout << "Question " << i+1 << "\n";
cin >> answerKey[i];
}
ifstream inFile("student.txt");
for(int i = 0; i < TEST_SIZE; i++)
{
inFile >> studentInfo[i].id;
inFile >> studentInfo[i].fName;
inFile >> studentInfo[i].lName;
for(int j = 0; j < TEST_SIZE; j++){
inFile >> studentInfo[i].testAnswers[j];
}
}
}
void calcGrade(char answerKey[], StudentInfo studentInfo[])
{
for(int i = 0; i < TEST_SIZE; i++)
{
for(int j = 0; j < TEST_SIZE; j++)
{
if(studentInfo[i].testAnswers[j] == answerKey[j])
{
studentInfo[i].totalPoints += 5;
}
studentInfo[i].avg = studentInfo[i].totalPoints * 2;
if(studentInfo[i].avg >= 90)
{
studentInfo[i].letterGrade = 'A';
}
else if(studentInfo[i].avg >= 80)
{
studentInfo[i].letterGrade = 'B';
}
else if(studentInfo[i].avg >= 70)
{
studentInfo[i].letterGrade = 'C';
}
else if(studentInfo[i].avg >= 60)
{
studentInfo[i].letterGrade = 'D';
}
else
{
studentInfo[i].letterGrade = 'F';
}
}
}
}
void bubbleSort(StudentInfo studentInfo[])
{
StudentInfo temp;
int i;
int j;
for(i = 0; i < (TEST_SIZE-1); i++)
{
for(j = 0; j < TEST_SIZE; j++)
{
if(studentInfo[j].lName < studentInfo[j-1].lName)
{
temp = studentInfo[j];
studentInfo[j] = studentInfo[j-1];
studentInfo[j-1] = temp;
}
}
}
}
void outputInfo(StudentInfo studentInfo[])
{
cout << setprecision(1) << fixed;
cout << "Student ID\tStudent Name\tAnswers\tTotal Pts\tAverage\t Letter Grade" << endl;
for(int i = 0; i < TEST_SIZE; i++)
{
cout << studentInfo[i].id << "\t";
cout << studentInfo[i].lName << " ";
cout << studentInfo[i].fName << "\t";
for(int j = 0; j < TEST_SIZE; j++)
{
cout << studentInfo[i].testAnswers[j];
}
cout << "\t" << studentInfo[i].totalPoints << "\t";
cout << studentInfo[i].avg << "\t";
cout << studentInfo[i].letterGrade << "\n";
}
}
I've tried everything within my meager abilities, but my program always crashes. Assumedly during the bubble sort since it works fine without that section. If someone could enlighten me as to where I erred I would be very grateful. Sorry for any inconvenience that I've caused.

Answer 1

What happens here
temp = studentInfo[j];
studentInfo[j] = studentInfo[j-1];
studentInfo[j-1] = temp;
when j==0? You access out of bounds. You're better off using std::swap from <algorithm> like
std::swap(studentInfo[j], studentInfo[j+1]);
making sure that you run j until TEST_SIZE - 1. Or write the "manual" swap but with j exchanged by j+1.