day-03.js

// https://adventofcode.com/2020/day/3

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`;

const textInputText = `
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`;

const slopes = [{
    right: 1,
    down: 1
}, {
    right: 3,
    down: 1
}, {
    right: 5,
    down: 1
}, {
    right: 7,
    down: 1
}, {
    right: 1,
    down: 2
}];

function parseInput(inputText) {
    return inputText.trim().split("\n");
}

function resolveStar1(input, slope) {
    const matrixInput = input.map(data => {
        return data.split('')
    });

    let x = 0;
    let y = 0;
    let threes = 0;

    const {right, down} = slope;

    while(y < input.length - 1) {

        x += right;
        if (x > matrixInput[y].length - 1) {
            x = x - matrixInput[y].length;
        }

        y += down;

        if (matrixInput[y][x] === '#') {
            threes += 1;
        }
    }

    return threes;
}

function resolveStar2(input, slopes) {
    const result = slopes.map(slope => {
        return resolveStar1(input, slope);
    });

    return result.reduce((prev, curr) => curr * prev, 1);
}

const input = parseInput(inputText);

const resultOne = resolveStar1(input, slopes[1]);
console.log(`For first star, # trees encountered = ${resultOne}`);

const resultTwo = resolveStar2(input, slopes);
console.log(`For second star, # trees encountered multiplied = ${resultTwo}`);