終極の図

struct Graph{
    struct Edge{
        int to, next; Graph *bel;
        inline int operator *(){ return to; }
        Edge& operator ++(){
            return *this=bel->edge[next]; }
    };
    void addedge(int x, int y){
        Edge &e=edge[++cntedge];
        e.to=y; e.next=fir[x];
        fir[x]=cntedge; e.bel=this;
    }
    void reset(){
        cntedge=0; memset(fir, 0, sizeof(fir)); }
    Edge& getlink(int x){
        return edge[fir[x]]; }
    Edge edge[maxm*2];
    int cntedge, fir[maxn];
}g;