The standard library provides a variety of functions for dealing with
containers such as vectors.  This example illustrates simple sorting and
searching a vector of objects.

// Sorting and searching in a vector of class instances

// If the vector is not too long, you could use find(), or iterate over the
// vector until you find a match.  However, if the if the vector is long, 
// it is better to sort it first, because it is a lot more efficient
// to find things in a sorted list.

// For complex objects like a class, you have to provide a function that
// specifies the sort order.

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

// We will be saving a lot of these in a vector
class Element {
	public:
	string name;
	string symbol;
	int atomic_number;
	
	Element(string name_in, string symbol_in, int atomic_number_in)
		: name(name_in), symbol(symbol_in), atomic_number(atomic_number_in)
		{}
		
	// By default, sort() etc. use this function, so we must define it
	bool operator<(const Element& e) const { return (atomic_number < e.atomic_number);}
};

// Alternative to operator< above is to provide this as final argument to sort, lower_bound, etc.
//bool element_smaller(Element e1, Element e2) {
//	return (e1.atomic_number < e2.atomic_number);
//}

// This gets filled by a lot of Elements in unspecified order
vector<Element> mytable;

// A little function to find elements by atomic number z
// This assumes that mytable has already been sorted.
void findelement(int z) {
	// The search functions like to return iterators:
	vector<Element>::iterator lower, upper, i;
	
	lower = lower_bound(mytable.begin(), mytable.end(), Element("Xxxx", "X", z));
	upper = upper_bound(mytable.begin(), mytable.end(), Element("Xxxx", "X", z));
	if (lower == upper) cout << "There is no element of atomic number " << z << endl;
	// Notice that upper is AFTER the last match
	else for (i = lower; i != upper; i++) {
		cout << i->symbol << " (list entry " << int(i - mytable.begin()) << ") has atomic number " << z << endl;
	}
}


int main() {
	Element e = Element("Actinium", "Ac", 89);
	mytable.push_back(e);
	e = Element("Aluminium", "Al", 13);
	mytable.push_back(e);
	e = Element("Antimony", "Sb", 51);
	mytable.push_back(e);
	e = Element("Argon", "Ar", 18);
	mytable.push_back(e);
	e = Element("Arsenic", "As", 33);
	mytable.push_back(e);
	e = Element("Astatine", "At", 85);
	mytable.push_back(e);
	e = Element("Avalon", "Av", 33);  
	mytable.push_back(e);

	cout << "Original order" << endl;
	for (int i=0; i < mytable.size(); i++) {
		cout << i << "\t" << mytable[i].atomic_number << "\t" << mytable[i].name << ", " << mytable[i].symbol << endl;
	}

	// Sort the vector using my custom comparison function
	sort(mytable.begin(), mytable.end());

	// Just for fun, print the vector this time using iterators
	cout << "Sorted order" << endl;
	for(vector<Element>::iterator i = mytable.begin(); i !=mytable.end(); i++) {
		cout << int(i-mytable.begin()) << "\t" << i->atomic_number << "\t" << i->name << ", " << i->symbol<< endl;
	}

	// Find elements with atomic number 33  (in my periodic table, there can be more than one)
	findelement(33);

	// Find elements with atomic number 17  (in my periodic table, there are none)
	findelement(17);

	// Find elements with atomic number 51 
	findelement(51);

}