adventofcode day 9

adventofcode.js

var distances = `London to Dublin = 464
London to Belfast = 518
Dublin to Belfast = 141`.split("\n");

var cities = {};
var shortest = {distance:null, route:null};

//Turn the inputs into objects
for (var i=0; i<distances.length; i++) {
  var distance = distances[i];

  var componenets = distance.match(/([a-zA-Z]+) to ([a-zA-Z]+) = (\d+)/);
  distance = parseInt(componenets[3]);
  add_place(componenets[1], componenets[2], distance );
  add_place(componenets[2], componenets[1], distance );
}

function add_place(place_a, place_b, distance) {
  if (!(place_a in cities)) cities[place_a] = {};
  cities[place_a][place_b] = distance;
}

// visit each city recursively
function visit(visiting_city, already_visited, distance_traveled) {

  already_visited.push(visiting_city);
  var at_end_of_tree = true;
  
  for (var next_city in cities[visiting_city]) {  
    if (already_visited.indexOf(next_city) == -1 ) {
      distance = cities[visiting_city][next_city];
      visit(next_city, already_visited.slice(), distance_traveled + distance);
      at_end_of_tree = false;
    }
  }

  if (at_end_of_tree) {
    if (shortest.distance == null | distance_traveled < shortest.distance) {
      shortest.distance = distance_traveled;
      shortest.route = already_visited.join(' -> ');
    }
  }
}

//begin by visiting each city
for (var starting_city in cities) {
  visit(starting_city, [], 0);
}

console.log(shortest);