11. Bitcoin "Mining"

РЕШЕНИЕ С FOR:

function bitcoin(input) {
    let sum = 0;
    let firstBuy = 0;

    for (let i = 1; i <= input.length; i++) {
        let currentSum = input[i - 1] * 67.51;

        if (i % 3 === 0) {
            currentSum *= 0.7;
        }
        sum += currentSum;

        if (firstBuy === 0 && sum >= 11949.16) {
            firstBuy = i;
        }
    }

    let bitcoins = Math.floor(sum / 11949.16);
    sum %= 11949.16;

    console.log(`Bought bitcoins: ${bitcoins}`);
    if (bitcoins !== 0) {
        console.log(`Day of the first purchased bitcoin: ${firstBuy}`);
    }
    console.log(`Left money: ${sum.toFixed(2)} lv.`);
}

РЕШЕНИЕ С ТЕРНАРЕН ОПЕРАТОР:

function bitcoin(input) {
    let sum = 0;
    let firstBuy = 0;

    for (let i = 1; i <= input.length; i++) {
        sum += input[i - 1] * 67.51 * (i % 3 === 0 ? 0.7 : 1);
        firstBuy += firstBuy === 0 && sum >= 11949.16 ? i : 0;
    }

    console.log(`Bought bitcoins: ${parseInt(sum / 11949.16)}\n${parseInt(sum / 11949.16) !== 0 ?
     `Day of the first purchased bitcoin: ${firstBuy}\n` : ''}Left money: ${(sum % 11949.16).toFixed(2)} lv.`);
}

РЕШЕНИЕ С WHILE, SHIFT() И ТЕРНАРЕН ОПЕРАТОР:

function bitcoin(input) {
    let sum = 0;
    let firstBuy = 0;
    let i = 1;

    while (input.length !== 0) {
        sum += input.shift() * 67.51 * (i % 3 === 0 ? 0.7 : 1);
        firstBuy += firstBuy === 0 && sum >= 11949.16 ? i : 0;
        i++;
    }

    console.log(`Bought bitcoins: ${parseInt(sum / 11949.16)}\n${parseInt(sum / 11949.16) !== 0 ?
     `Day of the first purchased bitcoin: ${firstBuy}\n` : ''}Left money: ${(sum % 11949.16).toFixed(2)} lv.`);
}