Connected Component in 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.)

S: DFS

dfs找到所有关联节点

/**
 * Definition for Undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    vector<vector<int>> connectedSet(vector<UndirectedGraphNode*>& nodes) {
        vector<vector<int>> result;
        for(const auto& node : nodes) {
            if (!visited[node->label]) {
                visited[node->label] = true;
                vector<int> curSet{node->label};
                dfs(node, curSet);
                sort(curSet.begin(), curSet.end());
                result.push_back(curSet);
            }
        }
        return result;
    }

    void dfs(UndirectedGraphNode* node, vector<int>& set) {
        for (const auto& i : node->neighbors) {
            if (!visited[i->label]) {
                visited[i->label] = true;
                set.push_back(i->label);
                dfs(i, set);
            }
        }
    }

private:
    unordered_map<int, bool> visited;
};