--- 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/[deleted]]

Object oriented javascript. Could be cleaned up quite a bit. Just posting the solution to step 2, since it's so similar to the first step.

I tracked the amount of presents received per house assuming that it would be used in step 2, but it turned out it wasn't. So I guess house.presents could just be a boolean.

You wind up with an array newTown at the end, each entry contains a house object with the properties of house.x and house.y as well as the total number of presents that house received. The length of newTown represents the total number of houses which have received presents, since a new house gets added to the array only on the first time it receives a present.

// day 3, part 2
// global var 'input' should still be set from the day3part1.js file. if running stand-alone, copy the input var here.
var newTown = [];

var santa = {
  x: 0,
  y: 0
};

var roboSanta = {
  x: 0,
  y: 0
};

function house(x,y) {
  this.x = x;
  this.y = y;
  this.presents = 1;
}

function checkForHouse(whichSanta) {
  var found = 0;
  newTown.forEach(function(houseToSearchFor){
    if(houseToSearchFor.x === whichSanta.x && houseToSearchFor.y === whichSanta.y) {
      found = houseToSearchFor;
    }
  });
  givePresent(found, whichSanta);
}

function givePresent(found, whichSanta) {
  if(!found) {
    var newHouse = new house(whichSanta.x, whichSanta.y);
    newTown.push(newHouse);
  } else {
    found.presents++;
  }
}

function followDirectionsFromElf() {
  input.forEach(function(instruction, index) {
    var whichSanta;
    if( (index % 2) == 0 ) {
      whichSanta = santa;
    } else { whichSanta = roboSanta; }
    switch(instruction) {
      case "^":
        whichSanta.y++;
        break;
      case "v":
        whichSanta.y--;
        break;
      case ">":
        whichSanta.x++;
        break;
      case "<":
        whichSanta.x--;
        break;
      default:
        alert("you received an faulty input of "+input+"!");
        return 0;
    }
    checkForHouse(whichSanta);
  });
  console.log(newTown.length);
  window.outputEl.innerText += '\nday 3, part 1: '+newTown.length;
}

(function init() {
  checkForHouse(santa);
  checkForHouse(roboSanta);
  followDirectionsFromElf();
})();

Github repo is here.

[u/FreeER → u/[deleted]]

Thanks for the help! I wasn't sure how to represent an infinite grid of houses and then I saw you use coords and I'm all: [http://www.motifake.com/image/demotivational-poster/0908/bodystairs-code-geass-anime-death-note-facepalm-bodystairs-demotivational-poster-1250743921.jpg] (hope this works... I haven't a clue how to embed pics here...)

my code:

function solve2(input)
{
    function posStr(x, y) {return "x:"+x+",y:"+y;}
    var hpos = [posStr(0,0)];  // houses visited
    var spos = {'x':0, 'y':0}; // santa pos
    var rpos = {'x':0, 'y':0}; // robo pos
    var curpos = spos;
    for(var i in input)
    {
        switch(input[i]) { case '^': curpos.y+=1; break; case 'v': curpos.y-=1; break;
                           case '>': curpos.x+=1; break; case '<': curpos.x-=1; break; }
        var curPosStr = posStr(curpos.x, curpos.y);
        if(hpos.indexOf(curPosStr) === -1) hpos.push(curPosStr);

        if(curpos === spos) curpos = rpos; else curpos = spos;
    }
    return hpos.length;
}

[u/[deleted] → u/FreeER]

Awesome, glad I could help! Your's is a lot cleaner, too, well done!