# Find the Connected Component in the Undirected Graph

Find the Connected Component in the Undirected Graph

Find the number connected component in the undirected graph. Each node in the graph contains a label and a list of its neighbors. (a connected component (or just component) of an undirected graph is a subgraph in which any two vertices are connected to each other by paths, and which is connected to no additional vertices in the supergraph.)

Example

Given graph:

```A------B  C
\     |  |
\    |  |
\   |  |
\  |  |
D   E```

Return `{A,B,D}, {C,E}`. Since there are two connected component which is `{A,B,D}, {C,E}`

Solution: BFS

```public List<List<Integer>> connectedSet(ArrayList<UndirectedGraphNode> nodes) {
List<List<Integer>> result = new ArrayList<>();
if (nodes == null || nodes.size() == 0) {
return result;
}
Queue<UndirectedGraphNode> q = new LinkedList<>();
q.offer(nodes.get(0));
List<Integer> component = new ArrayList<>();
Set<UndirectedGraphNode> visited = new HashSet<>();
while (!nodes.isEmpty()) {
if (q.isEmpty()) {
Collections.sort(component);
result.add(new ArrayList<>(component));
q.offer(nodes.get(0));
component = new ArrayList<>();
} else {
UndirectedGraphNode curr = q.poll();
if (!visited.contains(curr)) {
visited.add(curr);
nodes.remove(curr);
component.add(curr.label);
for (UndirectedGraphNode neighbor : curr.neighbors) {
q.offer(neighbor);
}
}
}
}
if (!component.isEmpty()) {
result.add(component);
}
return result;
}```