题解 | #整数与IP地址间的转换#

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

void (async function () {
    const sIp = await readline();
    console.log(ipToInt(sIp));
    const int = await readline();
    console.log(intToIp(int));
})();

function intToIp(int) {
    // 进进制串
    let b = toB(int);
    for (let i = 1, len = 32 - b.length; i <= len; i++) {
        b = "0" + b;
    }
    // console.log(b);
    const ip1 = b.substr(0, 8);
    const ip2 = b.substr(8, 8);
    const ip3 = b.substr(16, 8);
    const ip4 = b.substr(24, 8);
    // 转换成十进制
    return `${toInt(ip1)}.${toInt(ip2)}.${toInt(ip3)}.${toInt(ip4)}`;
}

function ipToInt(ip) {
    const arr = ip.split(".");
    // 解析成二进制
    const b = arr.map((num) => {
        let s = toB(num);
        for (let i = 1, len = 8 - s.length; i <= len; i++) {
            s = "0" + s;
        }
        return s;
    });
    // 连接起来
    const sTwo = b.join("");
    return toInt(sTwo);
}
function toInt(sTwo) {
    // console.log(sTwo);
    // 转换成十进制
    const total = sTwo
        .split("")
        .reverse()
        .map((char, i) => {
            return +char * 2 ** i;
        })
        .reduce((total, b) => {
            return total + b;
        }, 0);
    return total;
}
// 转换成二进制字符串
function toB(num) {
    const arr = [];
    while (num > 1) {
        arr.push(num % 2);
        num = +Math.floor(num / 2);
    }
    arr.push(num);
    return arr.reverse().join("");
}