POJ1511 Invitation Cards（多源单汇最短路）

边取反，从汇点跑单源最短路即可。

 #include<cstdio>
 #include<cstring>
 #include<queue>
 #include<algorithm>
 using namespace std;
 #define MAXN 1111111
 #define MAXM 1111111

 inline void in(int &ret){
     char c; ret=;
     while(c=getchar(),c<''||c>'');
     while(c>=''&&c<='') ret=ret*+c-'',c=getchar();
 }
 void out(long long x){
     if(x>) out(x/);
     putchar(x%+'');
 }

 struct Edge{
     int v,cost,next;
 }edge[MAXM<<];
 int head[MAXN],rhead[MAXN],NE;
 void addEdge(int a,int b,int c){
     edge[NE].v=b; edge[NE].cost=c; edge[NE].next=head[a];
     head[a]=NE++;
     edge[NE].v=a; edge[NE].cost=c; edge[NE].next=rhead[b];
     rhead[b]=NE++;
 }

 int n,m;
 int d[MAXN];
 bool vis[MAXN];
 void SPFA(){
     memset(d,,sizeof(d));
     d[]=;
     memset(vis,,sizeof(vis));
     vis[]=;
     queue<int> que;
     que.push();
     while(!que.empty()){
         int u=que.front(); que.pop();
         for(int i=head[u];i !=-; i=edge[i].next){
             int v=edge[i].v;
             if(d[v]>d[u]+edge[i].cost){
                 d[v]=d[u]+edge[i].cost;
                 if(!vis[v]){
                     vis[v]=;
                     que.push(v);
                 }
             }
         }
         vis[u]=;
     }
 }
 void rSPFA(){
     memset(d,,sizeof(d));
     d[]=;
     memset(vis,,sizeof(vis));
     vis[]=;
     queue<int> que;
     que.push();
     while(!que.empty()){
         int u=que.front(); que.pop();
         for(int i=rhead[u]; i!=-; i=edge[i].next){
             int v=edge[i].v;
             if(d[v]>d[u]+edge[i].cost){
                 d[v]=d[u]+edge[i].cost;
                 if(!vis[v]){
                     vis[v]=;
                     que.push(v);
                 }
             }
         }
         vis[u]=;
     }
 }

 int main(){
     int t,a,b,c;
     in(t);
     while(t--){
         NE=;
         memset(head,-,sizeof(head));
         memset(rhead,-,sizeof(rhead));
         in(n); in(m);
         while(m--){
             in(a); in(b); in(c);
             addEdge(a,b,c);
         }
         long long res=;
         SPFA();
         for(int i=; i<=n; ++i) res+=d[i];
         rSPFA();
         for(int i=; i<=n; ++i) res+=d[i];
         out(res); putchar('\n');
     }
     return ;
 }