Sort problem

[DEnumber50]

I am writing this program to sort the data and select a median from the information. It is giving me the error of sort is undefined. What would be the correct way to identify that? Also if the information could be put better from an experienced C++ user I am listening. Thanks for you help.

#include <iostream>
#include <vector>
#include <cstdio>
#include <iomanip>

using namespace std;

//Declaring Constants
const int ZERO = 0;
const int ONE_HUNDRED = 100;

int main()
{
	int firstExam, secondExam, thirdExam;
	int error;
	double median;
	vector<int> scores;
	size_t size = scores.size();

	cout << "Dr. DoLittle's Grading Program ..... (by Kirk Kelley)" << endl;
	do
	{
		error = 0;
		cout << "Please enter in the score for the first exam: ";
		cin >> firstExam;
		if (firstExam < 0 || firstExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> firstExam;
			cin.clear();
		}
	} while (error);
	do
	{
		error = 0;
		cout << "Please enter in the score for the second exam: ";
		cin >> secondExam;
		if (secondExam < 0 || secondExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> secondExam;
			cin.clear();
		}
	} while (error);
	do
	{
		error = 0;
		cout << "Please enter in the score for the third exam: ";
		cin >> thirdExam;
		if (thirdExam < 0 || thirdExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> thirdExam;
			cin.clear();
		}
	} while (error);

	//declaring variable
	int homework;

	//initiating loop
	while (!cin.eof())
	{

		homework = EOF;

		cout << "\nEnter score for homework assignment (press Ctrl+Z to quit): ";

		cin >> homework;

		if (!cin.good())
			if (homework == EOF)
				break;
			else
			{
				cout << "\nInvalid Input. Entry must be an integer." << endl;
				cin.clear();
				cin.ignore(std::numeric_limits<streamsize> ::max(), '\n');
			}
		else
		{
			if (homework >= ZERO && homework <= ONE_HUNDRED)
			{
				scores.push_back(homework);
			}
			else
			{
				cout << "\nInvalid Input. Grade must be between 0-100." << endl;
				cin.clear();
				cin.ignore(std::numeric_limits<streamsize> ::max(), '\n');
			}
		}
	}
	for (unsigned int i = 0; i < scores.size(); i++)
		{
			cout << "Scores: " << scores[i] << '\n';
			sort(scores.begin(), scores.end());
			if (scores.size() % 2 == 0)
			{
				median = (scores[size / 2 - 1] + scores[size / 2]) / 2.0;
			}
			else
			{
				median = scores[size / 2 - 1];
			}
		}
	cout << fixed << setprecision(2);
	cout << "Median: " << median << endl;
	cout << "First exam score: " << firstExam << endl;
	cout << "First exam score: " << secondExam << endl;
	cout << "First exam score: " << thirdExam << endl;
	system("Pause");
	return 0;
}

[Yanson]

#include <algorithm>

[DEnumber50]

That did work to declare the sort, but now I have a break. at the if else loop from 98 to 105. Wondering how to code it more effectively?

[MiiNiPaa]

First of all, move sort and median calculation out of your loop.
Second. If you need to find median, sort is not nesesarry. nth_element is enough.

[DEnumber50]

MiiNiPaa I am not sure what to put in the middle argument for nth_element, what should be put after scores.begin()? and also is the format outside the loop in the right spot?

#include <iostream>
#include <vector>
#include <cstdio>
#include <iomanip>
#include <algorithm>

using namespace std;

//Declaring Constants
const int ZERO = 0;
const int ONE_HUNDRED = 100;

int main()
{
	int firstExam, secondExam, thirdExam;
	int error;
	double median;
	vector<int> scores;
	size_t size = scores.size();

	cout << "Dr. DoLittle's Grading Program ..... (by Kirk Kelley)" << endl;
	do
	{
		error = 0;
		cout << "Please enter in the score for the first exam: ";
		cin >> firstExam;
		if (firstExam < 0 || firstExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> firstExam;
			cin.clear();
		}
	} while (error);
	do
	{
		error = 0;
		cout << "Please enter in the score for the second exam: ";
		cin >> secondExam;
		if (secondExam < 0 || secondExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> secondExam;
			cin.clear();
		}
	} while (error);
	do
	{
		error = 0;
		cout << "Please enter in the score for the third exam: ";
		cin >> thirdExam;
		if (thirdExam < 0 || thirdExam > 100)
		{
			cout << "Please enter a valid score between 0 and 100" << endl;
			cin >> thirdExam;
			cin.clear();
		}
	} while (error);

	//declaring variable
	int homework;

	//initiating loop
	while (!cin.eof())
	{

		homework = EOF;

		cout << "\nEnter score for homework assignment (press Ctrl+Z to quit): ";

		cin >> homework;

		if (!cin.good())
			if (homework == EOF)
				break;
			else
			{
				cout << "\nInvalid Input. Entry must be an integer." << endl;
				cin.clear();
				cin.ignore(std::numeric_limits<streamsize> ::max(), '\n');
			}
		else
		{
			if (homework >= ZERO && homework <= ONE_HUNDRED)
			{
				scores.push_back(homework);
			}
			else
			{
				cout << "\nInvalid Input. Grade must be between 0-100." << endl;
				cin.clear();
				cin.ignore(std::numeric_limits<streamsize> ::max(), '\n');
			}
		}
	}
	for (unsigned int i = 0; i < scores.size(); i++)
		{
			cout << "Scores: " << scores[i] << '\n';
		}
	nth_element(scores.begin(), scores.begin()+5, scores.end());
	if (scores.size() % 2 == 0)
	{
		median = (scores[size / 2 - 1] + scores[size / 2]) / 2.0;
	}
	else
	{
		median = scores[size / 2 - 1];
	}
	cout << fixed << setprecision(2);
	cout << "Median: " << median << endl;
	cout << "First exam score: " << firstExam << endl;
	cout << "First exam score: " << secondExam << endl;
	cout << "First exam score: " << thirdExam << endl;
	system("Pause");
	return 0;
}

[Yanson]

on line 18 size_t size = scores.size(); you calculate the size of the vector there is nothing in the vector at this point so size = 0;

on lines 102 and 106 you use size to calculate a vector subscript.
size / 2 - 1 size is 0 so the result will always be -1 which is not a valid subscript