Using the std::sort() Method

// STLSort.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <vector>
#include <algorithm>
#include <iostream>

typedef double DATE;

// Base class we're using to provide a function with a sortable value
class CHistoryItem
{
public:
	CHistoryItem(DATE rTimestamp)
	{	
		m_Timestamp = rTimestamp; 
	}

	// Return the time stamp value
	DATE& GetTimestamp()
	{	
		return m_Timestamp;	
	}

	// Indicate the item type as a string
	virtual	char* ItemName() = 0;

	// Output the item to a stream
	void OutputToStream(std::ostream& os)
	{
		os << ItemName() << "\t" << m_Timestamp << "\n";
	}

protected:
	DATE	m_Timestamp;
};


// Repair entry
class CRepairItem : public CHistoryItem
{
public:
	CRepairItem(DATE rTimestamp)
		: CHistoryItem(rTimestamp)
	{
	}

	// Indicate that this is a repair
	char* ItemName()	{	return "Repair: ";	}
};

// Installtion entry
class CInstallItem : public CHistoryItem
{
public:
	CInstallItem(DATE rTimestamp)
		: CHistoryItem(rTimestamp)	
	{	
	}

	// Indicate that this is a installation
	char* ItemName()	{	return "Install: ";	}
};

// Purchase entry
class CPurchaseItem : public CHistoryItem
{
public:
	CPurchaseItem(DATE rTimestamp)
		: CHistoryItem(rTimestamp)
	{
	}

	// Indicate that this is a installation
	char* ItemName()	{	return "Purchase: ";	}
};

///////////////////////////////

// A vector based class to contain our history items
class CHistoryVector : public std::vector<CHistoryItem*>
{
public:
	// Make sure that the history items are de-allocated so we don't leak
	~CHistoryVector()
	{
		for (iterator pItem=begin(); pItem != end(); ++pItem)
			delete *pItem;
	}
};

// Ascending date sorting function
struct SAscendingDateSort
{	
	bool operator()(CHistoryItem*& rpStart, CHistoryItem*& rpEnd)
	{
		return rpStart->GetTimestamp() < rpEnd->GetTimestamp();
	}
};

// Descending date sorting function
struct SDescendingDateSort
{	
	bool operator()(CHistoryItem*& rpStart, CHistoryItem*& rpEnd)
	{
		return rpStart->GetTimestamp() > rpEnd->GetTimestamp();
	}
};

// Stuff a vector with data & then sort
int main(int argc, char* argv[])
{
	CHistoryVector	HistoryVector;

	// Put two repair items in the vector
	HistoryVector.push_back(new CRepairItem(2*365.0));
	HistoryVector.push_back(new CRepairItem(5*365.0));

	// Now stick three installations items in the vector
	HistoryVector.push_back(new CInstallItem(3*365.0));
	HistoryVector.push_back(new CInstallItem (6*365.0));
	HistoryVector.push_back(new CInstallItem (4*365.0));

	// Finally we need to add a purchase item to the vector
	HistoryVector.push_back(new CPurchaseItem (1*365.0));

	//==================================
	// Sort the items in ascending order
	std::sort(HistoryVector.begin(), HistoryVector.end(), SAscendingDateSort());

	// Now show the results!
	std::cout << "Ascending Sort\n";
	for (long lEle=0; lEle < HistoryVector.size(); ++lEle)
		HistoryVector[lEle]->OutputToStream(std::cout);

	//==================================
	// Sort the items in descending order
	std::sort(HistoryVector.begin(), HistoryVector.end(), SDescendingDateSort());

	// Now show the new results!
	std::cout << "\nDescending Sort\n";
	for (lEle=0; lEle < HistoryVector.size(); ++lEle)
		HistoryVector[lEle]->OutputToStream(std::cout);


	getchar();	// Pause for a response
	return 0;
}