//graph adjacency corresponds to the index where it is assigned

class DFS {
public:
    int vertices;
    std::vector<std::vector<int>> graph;
    std::vector<int> visitedFlags;

    bool checkGraphConnected() {
        int startIndex = 0;
        visitedFlags = std::vector<int>(vertices, false);
        dfs(startIndex);
        return (std::find(visitedFlags.begin(), visitedFlags.end(), 0) == visitedFlags.end());
    }

    void dfs(int i) {
        if (!visitedFlags[i]) {
            visitedFlags[i] = true;
            for (int j = 0; j < graph[i].size(); j++) {
                dfs(graph[i][j]);
            }
        }
    }
};