问在c++中不使用双循环将对分组成多个集合

EN

int find_largest_component(const std::vector<std::pair<int,int>>& edge_list) {
    std::map<int, std::vector<int>> adjacency_list {};

    // build an adjecency list of the undirected graph
    for ( auto it : edge_list ) {
        adjacency_list[it.first].push_back(it.second);
        adjacency_list[it.second].push_back(it.first);
    }
    
    int component_count {0};
    int largest_component {0};

    // a queue for breadth first search
    std::queue<decltype(adjacency_list)::value_type> Q {};
    while ( !adjacency_list.empty() ) {

        // push a single node to queue and remove it from graph
        Q.push(std::move(*adjacency_list.begin()));
        adjacency_list.erase(adjacency_list.begin());

        while ( !Q.empty() ) {
            // pop a node from queue
            auto v = std::move(Q.front()); Q.pop();
            component_count++;

            // loop over neighbours
            for ( auto n : v.second ) {
                auto h = adjacency_list.find(n);
                if ( h != adjacency_list.end() ) {
                    // found a neighbour that is still in the graph
                    // (and thus not yes visited). Push it to the queue
                    // and remove it from the graph
                    Q.push(std::move(*h));
                    adjacency_list.erase(h);
                }
            }
        }

        // update the largest component count if we found a larger one
        if ( component_count > largest_component ) {
            largest_component = component_count;
        }
        component_count = 0;
    }

    return largest_component;
}