// *Permutation* by Krzysztof Bosak 1999-02-14

#include <stdio.h>
#include <string.h>
#include <assert.h>

class PermutateWord
{
	char *_buffer, *_reftab, *_maxtab;
	void per(char *tab)
	{
		char *temp1=_buffer+(tab-_reftab);
		*temp1=*tab;
		if(tab<_maxtab)
		{
			char *tab1=tab+1;
			char temp;
			per(tab1);
			for(char *xtab=tab1; xtab<=_maxtab; xtab++)
			{	
				temp=*tab;
				*tab=*xtab;
				*temp1=*tab;
				*xtab=temp;
				per(tab1);
				*xtab=*tab;
				*tab=temp;
			}
		}
		else
			puts(_buffer);
	}
	const PermutateWord& operator=(const PermutateWord&);
	PermutateWord(const PermutateWord&);
public:
	PermutateWord(char *tab)
	{
		_reftab=tab;
		char const l=static_cast<char>(strlen(tab));
		_buffer=new char[l+1];
		assert(_buffer);
		_buffer[l]='\0';
		_maxtab=tab+l-1;
		per(tab);
	}
	~PermutateWord()
	{
		delete[] _buffer;
	}
};

class Permutate
{
	char *_buffer, *_reftab, *_maxtab;
	void (*_function)(char*);
	void per(char *tab)
	{
		char *temp1=_buffer+(tab-_reftab);
		*temp1=*tab;
		if(tab<_maxtab)
		{
			char *tab1=tab+1;
			char temp;
			per(tab1);
			for(char *xtab=tab1; xtab<=_maxtab; xtab++)
			{	
				temp=*tab;
				*tab=*xtab;
				*temp1=*tab;
				*xtab=temp;
				per(tab1);
				*xtab=*tab;
				*tab=temp;
			}
		}
		else
			_function(_buffer);
	}
	const Permutate& operator=(const Permutate&);
	Permutate(const Permutate&);
public:
	Permutate(char len, void (*fun)(char*))
	{
		assert(len);
		assert(fun);
		_function=fun;
		_reftab=new char[len];
		assert(_reftab);
		for(char c=0; c<len; c++)
			_reftab[c]=c;
		_buffer=new char[len];
		assert(_buffer);
		_maxtab=_reftab+len-1;
		per(_reftab);
	}
	~Permutate()
	{
		delete[] _buffer;
		delete[] _reftab;
	}
};

void fun(char *index)
{
	printf("%d%d%d%d\n", index[0], index[1], index[2], index[3]);
}

int main()
{
	PermutateWord perword("abcdef");
	Permutate permut(4, fun);
	return 0;
}