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 }