题解 | #汽水瓶#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    // Write your code here
    let arr = []
    while(line = await readline()){
        arr.push(line)
    }
    arr.pop()
    let result = []
    for (let i = 0; i < arr.length; i++) {
        result.push(count(arr[i]))
    }
    result.forEach(item => console.log(item))
    function count(num) {
        if (num < 2) {
            return 0
        }
        if (num == 2) {
            return 1
        }
        // 得到可以换的瓶子个数
        let num1 = Math.floor(num / 3)
        // 得到余数
        let num2 = num % 3
        // 把换到的瓶子个数加上余数，进行下一轮的交换
        // 和上次交换的结果相加，就是最终交换的个数
        return num1 + count(num1 + num2)
    }
}()