Generator(1)

A.First Edition

This is the  first edition of my my Permutation Generator class. It is almost like a copy  from the algorithm 

from "Discrete Mathematics" into C++. I just do like a translating machine, cause I don't understand clearly 

about what is doing there. Just to release the boredness of life. I am really feeling a low-morale without 

coding. Later I add algorithm of generating combinations

B.Idea of program

1。 Basic idea: 

What else can a thief talk about the thing that he stole from others?

2。 Program design: 

I just make it a class and permutation is nothing but a sequence, so I give out the sequence index for the object to make a

"sequential permutation" (awkward?). I plan to give out my index array instead to handle the customer's object list. 

Actually when customer get the index, he know how to do it. Therefore, I finish my job. 

As for combination, you can see that each index of array is 1 for the element is in the set, or 0 for it is not. So, it is 

simple. and do you feel cheated?

3。 Major function

A. void slotMachine();

I like the name.

4。 Further improvement：

	A. I was in a hurry as there is a final exam of Probability this evening and I just feel extremely 

boring to be irresistable to do a little coding job. 

#include <iostream>

using namespace std;

const int MaxNumber =100;

class Generator
{
private:
	bool isCombination;
	int array[MaxNumber];
	int length;
	void nextGenerator();
	int nextDigit();
	int findSmallest(int next);
	void swapIndex(int a, int b);
	void formTail(int next);
	void output();
	void initialize(int number);
protected:
	void doGenerator();
	void doCombination();
public:
	Generator(int number =10, bool combination=false);
	void setLength(int number);
	int getLength() { return length;}	
	void slotMachine();
};


int main()
{
	Generator P(6);
	P.slotMachine();

	return 0;
}


void Generator::doCombination()
{
	int index =0;
	while (true)
	{
		while (array[index])
		{
			array[index] = 0;
			index++;
			if (index==length)
				return;
		}
		array[index] = 1;
		output();
		index =0;
	}
}

void Generator::doGenerator()
{
	int next =0;
	int small =0;
	while ((next = nextDigit()) != -1)
	{
		small = findSmallest(next);
		swapIndex(next, small);
		formTail(next);
		output();
	}
}

Generator::Generator(int number, bool combination)
{
	setLength(number);
	isCombination = combination;
	initialize(number);
}


void Generator::output()
{
	if (!isCombination)
	{
		cout<<"\nThis is the Permutation:\n";
	
	}
	else
	{
		cout<<"\nThis is the Combination:\n";
	}
	for (int i=0; i< length; i++)
	{
		cout<<array[i]<<(i==length - 1?";":",");
	}
}


void Generator::slotMachine()
{
	output();
	if (!isCombination)
	{
		doGenerator();
	}
	else
	{
		doCombination();
	}
}



void Generator::formTail(int next)
{
	int start = next +1;
	int end = length -1;
	while (end > start)
	{
		swapIndex(start, end);
		start++;
		end--;
	}
}

void Generator::swapIndex(int a, int b)
{
	int temp;
	temp = array[a];
	array[a] = array[b];
	array[b] = temp;
}

int Generator::findSmallest(int next)
{
	int small = length -1;
	while (array[next]> array[small])
	{
		small--;
	}
	return small;
}


void Generator::setLength(int number)
{
	if (number>1)
	{
		 length = number;		 
	}
}




int Generator::nextDigit()
{
	int next = length -2;
	while (array[next]> array[next+1])
	{
		next--;
		if (next<0)
		{
			return -1;
		}
	}
	return next;
}


void Generator::initialize(int number)
{
	if (!isCombination)
	{
		for (int i=0; i< length; i++)
		{
			array[i]= i;
		}
	}
	else
	{
		for (int i=0; i< length; i++)
		{
			array[i]= 0;
		}
	}
}

This is the permutation:
0,1,2,3;
This is the permutation:
0,1,3,2;
This is the permutation:
0,2,1,3;
This is the permutation:
0,2,3,1;
This is the permutation:
0,3,1,2;
This is the permutation:
0,3,2,1;
This is the permutation:
1,0,2,3;
This is the permutation:
1,0,3,2;
This is the permutation:
1,2,0,3;
This is the permutation:
1,2,3,0;
This is the permutation:
1,3,0,2;
This is the permutation:
1,3,2,0;
This is the permutation:
2,0,1,3;
This is the permutation:
2,0,3,1;
This is the permutation:
2,1,0,3;
This is the permutation:
2,1,3,0;
This is the permutation:
2,3,0,1;
This is the permutation:
2,3,1,0;
This is the permutation:
3,0,1,2;
This is the permutation:
3,0,2,1;
This is the permutation:
3,1,0,2;
This is the permutation:
3,1,2,0;
This is the permutation:
3,2,0,1;
This is the permutation:
3,2,1,0;

This is the Combination:
0,0,0,0;
This is the Combination:
1,0,0,0;
This is the Combination:
0,1,0,0;
This is the Combination:
1,1,0,0;
This is the Combination:
0,0,1,0;
This is the Combination:
1,0,1,0;
This is the Combination:
0,1,1,0;
This is the Combination:
1,1,1,0;
This is the Combination:
0,0,0,1;
This is the Combination:
1,0,0,1;
This is the Combination:
0,1,0,1;
This is the Combination:
1,1,0,1;
This is the Combination:
0,0,1,1;
This is the Combination:
1,0,1,1;
This is the Combination:
0,1,1,1;
This is the Combination:
1,1,1,1;