pipioj 1175: 货运费用（最短路）

 1 #define IO std::ios::sync_with_stdio(0)
 2 #include <bits/stdc++.h>
 3 using namespace  std;
 4 #define mk make_pair
 5 #define pb push_back
 6 const int inf=2147483647;
 7 const int N=1e5+10;
 8   
 9 struct node{
10     int u,w;
11     bool operator <(const node&p)const{
12         return w>p.w;
13     }
14 };
15   
16 vector<int>g[N],d[N];
17 int dis[N];
18 int n,m,s;
19 int vis[N];
20   
21 void dij(){
22     priority_queue<node>q;
23     fill(dis+1,dis+n+1,inf);
24     dis[1]=0;
25     vis[1]=1;
26     q.push(node{1,0});
27     while(!q.empty()){
28         node now=q.top();
29         q.pop();
30         int u=now.u;
31         if(now.w!=dis[u])continue;//优化，如果已经更新了与u相连的点通过u点到起点的距离那么无需再更新
32         for(int i=0;i<g[u].size();i++){
33             int v=g[u][i];
34             if(!vis[v]&&dis[u]+d[u][i]<dis[v]){
35                 vis[v]=1;
36                 dis[v]=dis[u]+d[u][i];
37                 q.push(node{v,dis[v]});
38             }
39         }
40     }
41 }
42 int main(){
43     IO;
44     cin>>n>>m>>s;
45     for(int i=1;i<=m;i++){
46         int u,v,w;
47         cin>>u>>v>>w;
48         if(w<s)continue;
49         if(m>400000)continue;
50         g[u].pb(v);
51         g[v].pb(u);
52         d[u].pb(1);
53         d[v].pb(1);
54     }
55     dij();
56     if(dis[n]<inf)cout<<dis[n]<<endl;
57     else cout<<-1<<endl;
58 }