Uva11374 Dijkstra

机场快线是市民从市内去机场的首选交通工具。机场快线分为经济线和商业线两种，线路、速度和价格都不同，你有一张商业线车票，可以坐一站商业线，而其他时候，只能乘坐经济线。假设换乘时间忽略不计，你的任务是找一条去机场最快的路线。

这样我们先从起点开始做一次dijkstra 然后在从终点开始做一次dijkstra， 然后枚举每个商业边。

#include <iostream>
#include <algorithm>
#include <string.h>
#include <cstdio>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
const int INF =;
const int maxn = +;
struct Edge{
  int from,to,dist;
};
struct HeapNoda{
   int d,u;
   bool operator <(const HeapNoda &rhs)const{
     return d>rhs.d;
   }
};
struct Dijkstra{
      int n,m;
      vector<Edge> edges;
      vector<int>G[maxn];
      bool done[maxn];
      int d[maxn];
      int p[maxn];
      void inti(int n){
        this->n=n;
        for(int i=; i<n; ++i) G[i].clear();
        edges.clear();
      }
      void AddEdge(int from, int to, int dist){
          edges.push_back((Edge){from,to,dist});
          m = edges.size();
          G[from].push_back(m-);
      }
      void dijkstra(int s){
          priority_queue<HeapNoda> Q;
          for(int i=; i<n; i++ ) d[i]=INF;
          d[s]=;
          memset(done,,sizeof(done));
          Q.push((HeapNoda){,s});
          while(!Q.empty()){
              HeapNoda x = Q.top(); Q.pop();
              int u = x.u;
              if(done[u]) continue;
              done[u] =true;
              for(int i=; i<G[u].size(); ++i){
                 Edge &e = edges[G[u][i]];
                 if(d[e.to]>d[u]+e.dist){
                      d[e.to] = d[u] +e.dist;
                      p[e.to] = G[u][i];
                      Q.push((HeapNoda){d[e.to],e.to});
                 }
              }
          }
      }
      void GetshortPaths(int s, int *dist, vector<int> *paths){
          dijkstra(s);
          for(int i=; i<n; i++){
              dist[i]=d[i];
              paths[i].clear();
              int t = i;
              paths[i].push_back(t);
              while(t!=s){
                  paths[i].push_back( edges[p[t]].from );
                  t = edges[ p[t] ].from;
              }
              reverse(paths[i].begin(),paths[i].end());
          }
      }
};
Dijkstra solver;
int d1[maxn], d2[maxn];
vector<int> paths1[maxn], paths2[maxn];
int main()
{
     int N,S,E,M,kase=,X,Y,Z,K;
     while(scanf("%d%d%d",&N,&S,&E) == ){
            S-- ; E--;
          scanf("%d",&M);
          solver.inti(N);
          for(int i=; i<M; ++i){
               scanf("%d%d%d",&X,&Y,&Z);X--; Y--;
               solver.AddEdge(X,Y,Z);
               solver.AddEdge(Y,X,Z);
          }
          solver.GetshortPaths(S,d1,paths1);
          solver.GetshortPaths(E,d2,paths2);
          int ans = d1[E];
          vector<int>path = paths1[E];
          int midpoint=-;
          scanf("%d",&K);
          for(int i=; i<K; ++i){
               scanf("%d%d%d",&X,&Y,&Z); X--; Y--;
               for(int j=; j<; j++){
                 if(d1[X]+d2[Y]+Z<ans){
                    ans=d1[X]+d2[Y]+Z;
                    path=paths1[X];
                    midpoint=X;
                    for(int a = paths2[Y].size()-; a>=; a--){
                        path.push_back( paths2[Y][a] );
                    }
                 }
                 swap(X,Y);
               }
          }
          if(kase) printf("\n");
          kase=;
          for(int i=; i<path.size()-; i++)
             printf("%d ",path[i]+);
          printf("%d\n",E+);
          if(midpoint==-) printf("Ticket Not Used\n");
          else printf("%d\n",midpoint+);
          printf("%d\n",ans);
     }
    return ;
}