题解 | #汽水瓶#

#include <iostream>
using namespace std;

int BottleNum(int Allnum)
{
    int n1    = Allnum / 3; //置换空瓶得到的饮料数
    int n1_re = Allnum % 3; //剩下空瓶，不足以置换饮料

    int num = n1;
    int Emptynum = n1 + n1_re;
    while (Emptynum >= 2){ //新饮料瓶 + 剩下空瓶，是否可以通过借空瓶来换
                             //2是因为只有两空瓶时，可向老板借1个，喝完还回去，此时手里没瓶子了。
        Emptynum = n1 + n1_re;
        n1       = (Emptynum) / 3; 
        n1_re    = (Emptynum) % 3; 

        if (n1 == 0 && n1_re == 2){
            num += 1;
            break;
        }
        num += n1;
        
    }
 
   
    return num;
}

int main() {
    int input;
    while (cin >> input){
        if (input > 0){
            cout << BottleNum(input) <<endl;
        }
    }
    return 0;
}