// SASSolver.h
// tom bailey   15 oct 04
// tom bailey   16 oct 08

// Declare a base class and several concrete classes of objects
//   that solve the best subarray sum problem for a sequence
//   stored in a vector.

#include <string>
using std::string;
#include <iostream>
using std::ostream;
#include <vector>
using std::vector;

class SASSolver
{
public:
	virtual double 
		bestSum( const vector<double> & ) = 0;

	virtual void 
		description( ostream & ) const;
};

SASSolver & getAlgorithm();

// prints a description of the algorithm
ostream & operator<<( ostream &, const SASSolver & );


// SASOne solves the problem using the simple, but slow, 
// technique of finding the sum of every possible segment
// of the container.
class SASOne: public SASSolver
{
public:
	// return the best sum for any subsequence in the vector.
	double 
	bestSum( const vector<double> & );

	void
	description( ostream & ) const;

private:
	template< typename IT >
	double
	sum( IT, IT );
};


// SASFour solves the same problem recursively by tracking 
// four attributes of a segment.

// ResType records and manipulates four attributes of a
// segment of a vector.

// ResType stores and manipulates the Results produced
//   by calls to the SASFour helper method used by the 
//   SASFour.bestSum method.
//   operator + combines the attributes for
//     two adjacent container segments into the 
//     attributes for one segment consisting of the
//     union of the two segments.
class ResType {
	double best;
	double sum;
	double bestToLeft;
	double bestToRight;
public:
	ResType();
	template< typename IT >
	ResType( IT );
	ResType operator += ( const ResType & );
	double bestSAS() const;
};

ResType operator + ( const ResType &, const ResType & );


class SASFour: public SASSolver
{
public:
	double 
	bestSum( const vector<double> & );

	void
	description( ostream & ) const;

private:
	template< typename IT >
	ResType	bestSum( IT, IT );
};