Cant understand why program ends

[wubbits]

So I am writing a program that takes test scores and students names, sorts them (together), averages them, and displays the sorted in ascending order with their names and the average of all the scores. This program inputs the data but does ends after the data is inputted. Everything seems right to me and I cant figure out whats wrong.

Thanks for any help!

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;

struct Data
{
	string Name;
	double Grade;
};

void getData(Data *, int);
void selectionSort(Data *, int);
double getAverage(Data *, int);
void displayData(Data *, int, double);

int main()
{
	Data *Test;
	double Average;		//average of the scores
	int Scores;			//number of scores

	//Get number of scores
	cout << "How many scores do you have to average? ";

	cin  >> Scores;

	// to hold the user-defined number of scores

	Test = new Data[Scores];

	getData(Test, Scores);
	selectionSort(Test, Scores);
	getAverage(Test, Scores);
	displayData(Test, Scores, Average);
	delete [] Test;
	Test = 0;
	
	return 0;
}
void getData(Data *Test, int Scores)
{
	cout << "Enter the names and scores for each student.\n";
	for(int i = 0; i < Scores; i++)
	{
		cout << "Student #" << (i + 1) << endl;
		cout << "   Name: ";
		cin.ignore();
		getline(cin, (Test + i)->Name);
		do
		{
			cout << "   Score :"; 
			cin  >> (Test + i)->Grade;
			if ((Test + i)->Grade < 0)
			{
				cout << "Scores must be greater than 0.\n"
					 << "Re-enter ";
			}
			cout << endl;
		} while ((Test + i)->Grade < 0);
	}
}
void selectionSort(Data *Test, int Scores)
{
	int startscan, minIndex;
	Data *minValue;
	for (startscan = 0; startscan < (Scores - 1); startscan++)
	{
		minIndex = startscan;
		*minValue = Test[startscan];
		for (int i = startscan + 1; i < Scores; i++)
		{
			if ((Test + i)->Grade < minValue->Grade)
			{
				*minValue = Test[i];
				minIndex = i;
			}
		}
		Test[minIndex] = Test[startscan];
		Test[startscan] = * minValue;
	}
} 
double getAverage(Data *Test, int Scores)
{
	double Total;
	double average;
	for (int i = 0; i < Scores; i++)
	{
		Total += (Test + i)->Grade;
	}
	average = Total / Scores;
	
	return average;
} 
void displayData(Data *Test, int Scores, double Avg) 
{
	cout << "    Test scores\n";
	cout << "Number of scores: " << Scores << endl;
	cout << "Scores in ascending-order:\n";
	for (int i = 0; i < Scores; i++)
	{
		cout << (Test + i)->Name << ": " << (Test + i)->Grade << endl;
	}
	cout << fixed << showpoint << setprecision(2);
	cout << "Average of scores: " << Avg << endl; 
}

[Peter87]

You have forgot to initialize Total in the getAverage function.

In selectionSort you are assigning to *minValue but minValue has not been initialized to point to any object. Perhaps you meant to make minValue point to the object, like so minValue = &Test[i]; ?

Average is uninitialized when being passed as argument to displayData on line 35.

[Peter87]

The way the program is written it first reads input from the user, then it prints the "data", and immediately after the program ends.

[wubbits]

When you say

Perhaps you meant to make minValue point to the object, like so minValue = &Test[i]; ?

do you mean to put it like this:

void selectionSort(Data *Test, int Scores)
{
	int startscan, minIndex;
	Data *minValue;
	for (startscan = 0; startscan < (Scores - 1); startscan++)
	{
		minIndex = startscan;
		*minValue = Test[startscan];
		for (int i = startscan + 1; i < Scores; i++)
		{
			if ((Test + i)->Grade < minValue->Grade)
			{
				minValue = &Test[i];
				minIndex = i;
			}
		}
		Test[minIndex] = Test[startscan];
		Test[startscan] = * minValue;
	}
} 

I tried this and it still fails

[Peter87]

Yes, but that line was just an example. You would also need to make the same change on line 70.

After you have made these changes both Test[minIndex] and *minValue will give you the same array element so it is a bit unnecessary that you have both minIndex and minValue in the program. One of them is enough.

Note the swap code on line 79-80 will not be correct. Perhaps it's more obvious why if it is rewritten without using minValue.

Test[minIndex] = Test[startscan];
Test[startscan] = Test[minIndex];