iveney/enumeration usage example.cpp

## enumeration usage example.cpp
enum label{A,B,C,D,E,N};	// N is exactly the size
char * desc="ABCDE"

vector<int> v(N);
// do sth.
cout << desc[A] << "'s value is " << v[A] << endl;
	enum label{A,B,C,D,E,N}; // N is exactly the size
	char * desc="ABCDE"

	vector<int> v(N);
	// do sth.
	cout << desc[A] << "'s value is " << v[A] << endl;