The network of roads in the village forms a graph. A graph is a collection of points (places in the village) with lines between them (roads). This graph will be the world that our robot moves through. The array of strings isn’t very easy to work with. What we’re interested in is the destinations that we can reach from a given place. Let’s convert the list of roads to a data structure that, for each place, tells us what can be reached from there. function buildGraph(edges) { let graph = Object.create(null); function addEdge(from, to) { if (graph[from] == null) { graph[from] = [to]; } else { graph[from].push(to); } } for (let [from, to] of edges.map(r => r.split("-"))) { addEdge(from, to); addEdge(to, from); } return graph; } const roadGraph = buildGraph(roads);
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