题解：最短路模板题
#include <cstdio>
#include <utility>
#include <cstring>
#include <queue>
using namespace std;
const int N=20005;
const int INF=9999999;
typedef pair<int,int>seg;
priority_queue<seg>,vector<seg>,greater<seg> >q;
int d[N],head[N],u[N],v[N],w[N],next[N],n,m,a,b,c;
bool vis[N];
void build(){
memset(head,-1,sizeof(head));
for(int e=1;e<=m;e++){
scanf("%d%d%d",&u[e],&v[e],&w[e]);
u[e+m]=v[e]; v[e+m]=u[e]; w[e+m]=w[e];
next[e]=head[u[e]]; head[u[e]]=e;
next[e+m]=head[u[e+m]]; head[u[e+m]]=e+m;
}
}
void Dijkstra(int src){
memset(vis,0,sizeof(vis));
for(int i=1;i<=n;i++) d[i]=INF;
d[src]=0;
q.push(make_pair(d[src],src));
while(!q.empty()){
seg now=q.top(); q.pop();
int x=now.second;
if(vis[x]) continue; vis[x]=true;
for(int e=head[x];e!=-1;e=next[e])
if(d[v[e]]>d[x]+w[e]){
d[v[e]]=d[x]+w[e];
q.push(make_pair(d[v[e]],v[e]));
}
}
}
int main(){
while(~scanf("%d%d",&n,&m)&&n+m){build();Dijkstra(1);printf("%d
",d[n]);}
return 0;
}