AdventOfCode2020/Day 3/luke.js

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const dataLines = input.split("\n");

function formatDataLine(dataLine) {
    return dataLine.split("");
};

const map = dataLines.map(formatDataLine);

const mapHeight = map.length;
const mapWidth = map[0].length;
const pointer = [0,0];

function step(pointer, map, goRight, goDown) {
    const x = pointer[0];
    const y = pointer[1];
    let newX = x + goRight;
    let newY = y + goDown;
    if (newX > (mapWidth - 1)) {
        newX = newX - mapWidth;
    }
    pointer[0] = newX;
    pointer[1] = newY;
    // has to do y then x. [ row[col, col], ... ]
    return map[pointer[1]][pointer[0]];
}

let treeCount = 0;
while(pointer[1] < (mapHeight - 1)) {
    const land = step(pointer, map, 3, 1);
    if (land === "#") treeCount++;
}

console.log(treeCount);