Dijkstra

# define INF ULLONG_MAX
ull mn=INF;
class Graph
{
    ull V;    
     list< pair<ull, ull> > *adj;
 
    public:
    Graph(ull V);  
    void addEdge(ull u, ull v, ull w);
    void shortestPath(ull s,vector<ull>&dist,ull k);
};

Graph::Graph(ull V)
{
    this->V = V;
    adj = new list< pair<ull, ull> >[V];
}
 
void Graph::addEdge(ull u, ull v, ull w)
{
    adj[u].push_back(make_pair(v, w));
    adj[v].push_back(make_pair(u, w));
}
void Graph::shortestPath(ull src,vector<ull>&dist,ull k)
{
    
    set< pair<ull, ull> > setds;
    setds.insert(make_pair(dist[src], src));
    while (!setds.empty())
    {
        pair<ull, ull> tmp = *(setds.begin());
        setds.erase(setds.begin());
        ull u = tmp.second;
        list< pair<ull, ull> >::iterator i;
        for (i = adj[u].begin(); i != adj[u].end(); ++i)
        {
            ull v = (*i).first;
            ull weight = (*i).second;
            
            if (dist[v] > dist[u] + weight)
            {
                if (dist[v] != INF && setds.find(make_pair(dist[v], v))!=setds.end())
                    setds.erase(setds.find(make_pair(dist[v], v)));
                dist[v] = dist[u] + weight;
                setds.insert(make_pair(dist[v], v));
            }
        }
    }
}
int main()
{
  int V;
  cin>>V;
  vector<int>dist(V,INF);
  Graph g(V);
  g.add(a,b,x);
  g.shortestpath(s,dist);
}