BFS template

gistfile1.txt

private List<String> bfs(Map<String, Set<String>> graph, Set<String> visited, String start) {
        if (visited.contains(start)) return Collections.emptyList();

        List<String> emails = new ArrayList<>();
        Queue<String> queue = new LinkedList<>();
        queue.offer(start);
        visited.add(start);
        while (!queue.isEmpty()) {
            int size = queue.size();

            for (int i = 0; i < size; i++) {
                String node = queue.poll();
                emails.add(node);

                Set<String> neighbors = graph.get(node);
                for (String neighbor : neighbors) {
                    if (visited.contains(neighbor)) continue;

                    queue.offer(neighbor);
                    visited.add(neighbor);
                }
            }
        }

        return emails;
    }