题解 | #进制转换#

const readline = require("readline");

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.on("line", function (line) {
    console.log(hexToDecimal(line));
});

function hexToDecimal(hex: string): number {
    // 移除十六进制前缀 '0x'（如果存在）
    hex = hex.startsWith("0x") ? hex.slice(2) : hex;

    const hexDigits = "0123456789ABCDEF";
    let decimal = 0;

    // 从右往左遍历十六进制字符串
    for (let i = hex.length - 1; i >= 0; i--) {
        const digit = hexDigits.indexOf(hex[i].toUpperCase());
        // 将每位的十六进制位与其相应的权值相乘，然后累加
        decimal += digit * Math.pow(16, hex.length - 1 - i);
    }

    return decimal;
}