/*
	C++ style program

		use vector, sort(), iostreams

	read or generate N numbers
	optionally sort them


	- Bjarne Stroustrup - http://www.research.att/~bs

*/

#include<vector>
#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;



/*
	command line argument handling:

		prog 1		- read from cin and sort 

		prog 0		- read from cin (don't sort)

		prog 1 file	- read from file and sort

		prog 0 file	- read from file (don't sort)

		prog 1 5000000	- generate 500,000 elements and sort

		prog 0 5000000	- generate 500,000 elements (don't sort)
		
	an optional 3rd argument controls preallocation.
*/

int main(int argc, char* argv[])
{
	int max = 0;	// by default: read from cin
	int res = 1000;	// by default: grow incrementally
	bool s = true;	// by default: sort
	char* file = 0;

	switch (argc) {	// s { max | file } res
	case 4:
		res = atoi(argv[3]);
	case 3:
		max = atoi(argv[2]);
		if (max == 0) file = argv[2];
	case 2:
		s = atoi(argv[1]);
		break;
	default:
		cerr << "wrong number of arguments\n";
		exit(1);
	} 

	vector<double> buf;
	buf.reserve(res);	// logically redundant; for efficiency only

	double d;
	double median = 0;
	double mean = 0;

	if (max) {
		cout << argv[0] << ": C++ style generate " << max << endl;
		for (int i = 0; i<max; i++) {
			d = double(rand()%10000)/100;
			buf.push_back(d);
			mean = (buf.size()==1) ? d : mean+(d-mean)/buf.size();	// prone to rounding errors
		}
	}
	else if (file) {
		fstream fin(file,ios::in);

		cout << argv[0] << ": C++ style read " << file << endl;
		while(fin>>d) {
			buf.push_back(d);
			mean = (buf.size()==1) ? d : mean+(d-mean)/buf.size();	// prone to rounding errors
		}
	}
	else {
		cout << "read cin\n";
		while(cin>>d) {
			buf.push_back(d);
			mean = (buf.size()==1) ? d : mean+(d-mean)/buf.size();	// prone to rounding errors
		}
	}

	if (s) {
		cout << "sort\n";	
		sort(buf.begin(),buf.end());
	}

	if (buf.size()) {
		int mid = buf.size()/2;
		median = (buf.size()%2) ? buf[mid] : (buf[mid-1]+buf[mid])/2;
	}

	cout << "number of elements = " << buf.size()
		<< ", median = " << median
		<< ", mean = " << mean << endl;

}