题解 | 汽水瓶

#include <stdio.h>
void calTotalNum(int bottleNum, int* totalSodaNum);

int main() {
    int n;
    int totalSodaNum;
    while (scanf("%d", &n) != EOF) {
        if (n == 0) {
            break;
        }
        totalSodaNum = 0; // 每次需要重置为 0
        calTotalNum(n, &totalSodaNum);
        printf("%d\n", totalSodaNum);
    }
    return 0;
}

// 递归函数，明确退出条件
void calTotalNum(int bottleNum, int* totalSodaNum)
{
    int extraSoda = bottleNum / 3;   // 兑换后得到的汽水
    int extraBottle = bottleNum % 3; // 兑换后剩余的空瓶
    int curBottle = extraSoda + extraBottle; // 喝完汽水后的总瓶子
    
    *totalSodaNum += extraSoda;
    //printf("--- + %d = %d   %d\n", extraSoda, *totalSodaNum, curBottle);

    if (curBottle >= 3) {
        return calTotalNum(curBottle, totalSodaNum);
    }

    if (curBottle == 2) {
        *totalSodaNum += 1; // 当前有两个瓶子，可以借一个兑换后还一个
        // printf("*** + %d = %d\n", 1, *totalSodaNum);
        return;
    }

    if (curBottle == 1) { // 当前有1个瓶子，不能继续兑换
        return;
    }
}