/**
*500個小孩兒，每次數三個人，第三個人離開。
*最後剩下的是第幾個小孩兒
*數三退一
*/
public class Count3Quit
{
	public static void main (String[] args)
	{
		boolean[] arr =new boolean [500];
		for (int i=0;i<=arr.length-1;i++)
		{
			arr[i] = true;
		}
		
		int leftCount = arr.length;
		int countNum = 0;
		int index = 0;
		while(leftCount>1)
		{
			if (arr[index] == true)
			{
				countNum++;
				if (countNum==3)
				{
					countNum=0;
					leftCount--;
					arr[index]=false;
				}
			}
			index ++;
			
			if (index ==arr.length)
			{
				index = 0;
			}
		}
		
		for(int i=0;i<arr.length;i++)
		{
			if (arr[i]==true )
			{
				System.out.println(i);
			}
		}
	}
}
 

/**
*面向物件思路
*/
public class Count3Quit2
{
	public static void main (String[] args)
	{
		KidCircle kc =new KidCircle(500);
		int countNum = 0;
		Kid k = kc.first;
		while(kc.count >1)
		{
			countNum ++;
			if (countNum == 3)
			{
				countNum =0;
				kc.delete(k);
			}
			k = k.right;
		}
		System.out.println(kc.first.id);
	}
}

 class Kid
 {
	int id;
	Kid left;
	Kid right;
 }
 
 class KidCircle
 {
	int count = 0;
	Kid first,last;
	KidCircle(int n)
	{
		for (int i=0;i<n;i++)
		{
			add();
		}
	}
	
	void add()
	{
		Kid k = new Kid();
		k.id=count;
		
		if (count <= 0)
		{
			first = k;
			last = k;
			k.left= k;
			k.right = k;
		}
		else
		{
			last.right = k;
			k.left =last;
			k.right = first;
			first.left = k;
			last = k;
		}
		count ++;
	}
	
	void delete(Kid k)
	{
		if (count <= 0)
		{
			return ;
		}
		else if( count==1)
		{
			first = last =null;
		}
		else
		{
			k.left.right=k.right;
			k.right.left=k.left;
			if (k==first)
			{
				first =k.right ;
			}
			else if (k==last)
			{
				last =k.left;
			}
		}
		count--;
	}
 }