编程 折纸问题

请把纸条竖着放在桌⼦上，然后从纸条的下边向上⽅对折，压出折痕后再展开。此时有1条折痕，突起的⽅向指向纸条的背⾯，这条折痕叫做“下”折痕 ；突起的⽅向指向纸条正⾯的折痕叫做“上”折痕。如果每次都从下边向上⽅ 对折，对折N次。请从上到下计算出所有折痕的⽅向。给定折的次数n,请返回从上到下的折痕的数组，若为下折痕则对应元素为"down",若为上折痕则为"up"。

1.

class FoldPaper {public:    vector<string> foldPaper(int n) {        // write code here        fold(n, true);        return vec;    }         void fold(int n, bool isDown){        if(n==0)            return;        fold(n-1, true);        if(isDown)            vec.push_back("down");        else            vec.push_back("up");        fold(n-1, false);    }         vector<string> vec;};

2.

class FoldPaper{public:    vector<string> foldPaper(int n)    {        foldN(1, n, true);        return vStr;    }          void foldN(int i, int n, bool isDown)    {        if (i > n)            return;        foldN(i+1, n, true);        if (isDown)            vStr.push_back("down");        else            vStr.push_back("up");        foldN(i+1, n, false);    }private:    vector<string> vStr;};