Add solutions to day 12 in javascript.

2017/README.md

@@ -18,7 +18,7 @@ The current plan, in no particular order:
 - [x] Kotlin - [Day 10](./day-10/solution.kt)
 - [x] Lex - [Day 09](./day-09/solution.l)
 - [x] Matlab - [Day 06](./day-06)
-- [ ] Node.js
+- [x] Node.js - [Day 12](./day-12/solution.js)
 - [ ] Objective C
 - [x] Perl - [Day 05](./day-05/solution.pl)
 - [ ] PHP

2017/day-12/solution.js

@@ -0,0 +1,70 @@
+const stdin = process.openStdin();
+let content = '';
+
+Set.prototype.union = function(setB) {
+	var union = new Set(this);
+	for (var elem of setB) {
+		union.add(elem);
+	}
+	return union;
+}
+
+function parseConnections(data) {
+	let connections = {};
+
+	data.split("\n").forEach(line => {
+		if (!line) {
+			return;
+		}
+
+		let from, to;
+		[from, to] = line.split(" <-> ");
+		connections[from] = to.split(", ");
+	});
+
+	return connections;
+}
+
+function getConnected(from, connections) {
+	let todo = [from];
+	let connected = new Set(todo);
+
+	for (let cur = 0; cur < todo.length; ++cur) {
+		if (!connections[todo[cur]]) {
+			continue;
+		}
+
+		connections[todo[cur]].forEach(n => {
+			if (!connected.has(n)) {
+				connected.add(n);
+				todo.push(n);
+			}
+		});
+	}
+
+	return connected;
+}
+
+stdin.addListener('data', d => {
+	content += d.toString();
+});
+
+stdin.addListener('end', () => {
+	let connections = parseConnections(content);
+
+	let connected = getConnected("0", connections);
+
+	console.log(connected.size);
+
+	let groups = 1;
+
+	for (let n in connections) {
+		if (connected.has(n)) {
+			continue;
+		}
+
+		connected = connected.union(getConnected(n, connections));
+		++groups;
+	}
+	console.log(groups);
+});