bfs

void bfs(int i){
    for(int j = 0; j < 9; j++){
        visited[j] = 0;
        parent.push_back(-1);
    }
    queue<int> Q;
    visited[i] = 1;
    Q.push(i);

    while(Q.size() != 0){
        int a = Q.front();
        Q.pop();
        for(int k = 0; k < E[a].size(); k++) {
            int s = E[a][k];
            if(visited[s] == 0){
                visited[s] = 1;
                parent[s] = a;
                Q.push(s);
            }
        }
    }
}