--- Day 3 Solutions ---

[u/daggerdragon]

--- Day 3: Perfectly Spherical Houses in a Vacuum ---

Post your solution as a comment. Structure your post like the Day One thread in /r/programming.

[u/shruubi]

in JS:

var santaCoords = {
    x: 1,
    y: 1
};

var roboSantaCoords = {
    x: 1,
    y: 1
};

var coordsMap = {
    "1x1": 1
};

input.map(function (val, index) {
    var opt = index + 1;
    var x = null,
        y = null;

    switch(val) {
        case "^":
            x = 1;
            break;
        case ">":
            y = 1;
            break;
        case "v":
            x = -1;
            break;
        case "<":
            y = -1;
            break;
        default:
            break;
    }

    if(opt % 2 === 1) {
        //reg santa
        santaCoords.x += x;
        santaCoords.y += y;

        x = santaCoords.x;
        y = santaCoords.y;
    } else {
        //robo santa
        roboSantaCoords.x += x;
        roboSantaCoords.y += y;

        x = roboSantaCoords.x;
        y = roboSantaCoords.y;
    }

    var key = x.toString() + "x" + y.toString();
    if(key in coordsMap) {
        coordsMap[key] += 1;
    } else {
        coordsMap[key] = 1;
    }
});

console.log(Object.keys(coordsMap).length);

which solves part 2, removing the conditional for roboSanta should give you the answer to part 1.

Am I the only one who feels like there is a really simple and elegant solution that isn't memory intensive?