int V;

int E;

vector<vector<int>> adj; //邻接链表

void addEdge(int v,int w){

adj[v].push_back(w); //区别于无向图

}

Digraph(int v):V(v),E(0){adj.resize(v,vector<int>());};

Digraph(string file){

std::ifstream infile(file);

string tmp;

int lineNum = 0;

while(std::getline(infile,tmp)){

std::istringstream iss(tmp);

int v1,v2;

if(lineNum==0) {iss>>V; adj.resize(V,vector<int>());}

else if(lineNum==1) iss>>E;

else {

iss>>v1>>v2;

addEdge(v1,v2);

}

lineNum++;

}

};

int getV(){return V;}

int getE(){return E;}

int degree(int v){return adj[v].size();}

vector<int> getadj(int v){return adj[v];}

//反转图

Digraph* reverseG(){

Digraph* revG = new Digraph(V);

for(int v=0;v<V;v++){

for(int w : getadj(v))

revG->addEdge(w,v);

}

return revG;

}