Why my simple bector produces the wrong result ?

[pieroborrelli]

Hello, I'm a C++ beginner and I'm trying to my program (I copied the code from the book : programming principles and practice using C++). This is the code :

// calculate mean and median temperatures 
int main()
{
	vector<double> temps; 
	for (double temperatures; cin >> temperatures;)
		temps.push_back(temperatures); 

	// calculate mean temperature
	double sum = 0; 
	for (double x : temps) sum += x; 
	cout << "The average temperature is : " << sum / temps.size() << "\n"; 

	// calculate median temperature 
	sort(temps); 
	cout << "The median temperature is : " << temps[temps.size() / 2 ] << "\n";  


	return 0; 

}

My problem is with the median, the book specify that that's not an appropriate way to calculate the median but for this program it will be ok. If I test the program with the value 2.2 and 3.5 for example I get the value of the mean (ok) and the value of the median, the problem is that sometimes the value of the median is wrong.

If I enter 2 values in input for example, the value of the median should be the element of the vector wich has the index equal to the value of size() / 2. If I enter 6.6 and 1.4 and I terminate the input with end-of file the size should be 2, and the median should be 2 / 2 == 1; So why i get the elemet of the vector with value 0 ? Am I misunderstanding something ?

[Peter87]

Note that you sort the vector so I guess 1.4 will be at index 0 and 6.6 at index 1.