PROGRAMMING GRIDS 木棍正方形

前面用迭代不知道为什么出错，后来改用递归

算法思想：

首先若木棒长度和不是4的整数倍则不可能构成正方形，逐条边填充，如遇到一条边不能填充则CUT

考虑几种分支情况：

如果当前边剩余空间为0

若剩余木棒也为0，则已经填充完毕（此时一定恰好填充了4条边）

否则填充下一条边

对每条边设立使用标记，从未使用的第一条边开始逐个填入，填入时将访问标记设为true（之后归还），递归填其余边

如果剩余木棒可以填充在剩余空间中，则直接返回TRUE

如果不能填充，取消当前木棒，若当前木棒已经填满某条边，则其余木棒不用再填充（取掉之后也一样）

如果下一条木棒和当前木棒相同，则也不用比较

代码：

# include 
# include 
# include 
# include 

using namespace std;

int EdgeLength = 0;
vector stickStorage;
vector usage;

bool pathFinder(int stickRemain, int spaceRemain, int subscription)
{
	int spcR = spaceRemain;
	int stkR = stickRemain;
	if ( spaceRemain == 0 )
	{
		if ( stickRemain == 0 )
		{
			return true;
		}
		spcR = EdgeLength;
		subscription = 0;
	}
	int size = stickStorage.size();
	for ( int i = subscription ; i < size; i++ )
	{
		if ( usage[i] == false && stickStorage[i] <= spcR )
		{
			usage[i] = true;
			if ( pathFinder(stkR-1,spcR-stickStorage[i],i+1) )
			{
				return true;
			}
			usage[i] = false;
			if ( stickStorage[i] == spcR || spcR == EdgeLength )	//If the current stick fills a line, there's no need to compare any more
			{
				break;
			}
			while ( stickStorage[i] == stickStorage[i+1] && i < size-1 )
			{
				i++;
			}
		}
	}
	return false;
}

int main()
{
	int n = 0;
	int stickNum = 0;
	int currentStickLen = 0;
	bool possible = false;
	int sum = 0;
	
	cin >> n;

	int j = 0;
	for ( int i = 0; i < n; i++ )
	{
		possible = false;
		EdgeLength = 0;
		sum = 0;
		stickStorage.clear();
		usage.clear();
		cin >> stickNum;
		for ( j = 0; j < stickNum; j++ )
		{
			cin >> currentStickLen;
			sum += currentStickLen;
			stickStorage.push_back(currentStickLen);
			usage.push_back(false);
		}
		sort(stickStorage.begin(),stickStorage.end(),greater());
		if ( sum%4 != 0 )
		{
			possible = false;
		}
		else
		{
			EdgeLength = sum/4;
			possible = pathFinder(stickStorage.size(),EdgeLength,0);
		}
		if ( possible )
		{
			cout << "yes" << endl;
		}
		else 
		{
			cout << "no" << endl;
		}
	}
	return 0;
}