//
// Example of using STL functions and classes.
//
// Program to compute, for a sequence of doubles,
//   their average, variance, and median.
//
// Average = sum of all elements / number of elements
// 
// Variance = sum over all elements v[i] of (v[i] - average) squared.
//
// Median = number m such that equal numbers of v[i]'s are smaller and
//   larger than m -- i.e., the number "in the middle".
//

#include <iostream.h>
#include <stdlib.h>             // has EXIT_SUCCESS
#include <algorithm>		// has sort()
#include <numeric>		// has accumulate()
#include <vector>

int main(void) {

  cout << "Enter some numbers, ctrl-D to end:\n";

  vector<double> v;

  double temp;

  while (cin >> temp)
    v.push_back(temp);

  // Compute and print average using STL accumulate().
  double average = accumulate(v.begin(), v.end(), 0.0) / v.size();
  cout << "Average = " << average << endl;

  // Compute and print variance using loop with STL iterator.
  double variance = 0.0;
  for (vector<double>::const_iterator pos = v.begin(); pos != v.end();
       ++pos)
    variance += ((*pos) - average)*((*pos) - average);
  cout << "Variance = " << variance << endl;

  // Compute and print median using STL sort().
  sort(v.begin(), v.end());
  int lng = v.size();
  if ((lng % 2) == 0)
    // if size is even, there are two middle elements, and median
    // is their average.
    cout << "Median = " << (v[lng/2-1] + v[lng/2])/2 << endl;
  else
    cout << "Median = " << v[lng/2] << endl;

  return EXIT_SUCCESS;
}