1 #include <cstdio>
2 #include <cmath>
3 #include <cstring>
4 #include <algorithm>
5 #include <queue>
6 #include <stack>
7 #include <vector>
8 #include <iomanip>
9 using namespace std;
10 typedef pair<int,int> P;
11 const int mmax=160000;
12 struct edge{
13 int next,to,w;
14 }e[mmax];
15 int n,m,d[mmax],head[mmax],cnt;
16 void add(int u,int v,int d)
17 {
18 e[cnt].w=d;
19 e[cnt].to=v;
20 e[cnt].next=head[u];
21 head[u]=cnt++;
22 }
23 int main(int argc, char *argv[])
24 {
25 while(scanf("%d%d",&n,&m)!=EOF)
26 {
27 memset(head,-1,sizeof(head));
28 fill(d+1,d+1+n,0x3f3f3f3f);
29 cnt=0;
30 for(int i=0;i<m;i++)
31 {
32 int x,y,z;
33 scanf("%d%d%d",&x,&y,&z);
34 add(x,y,z);
35 }
36 d[1]=0;
37 priority_queue<pair<int,int> >q;
38 q.push(make_pair(-d[1],1));
39 while(!q.empty())
40 {
41 P p=q.top();
42 int now=p.second;
43 q.pop();
44 if(-p.first>d[now])continue;
45 for(int i=head[now];i>=0;i=e[i].next)
46 {
47 int v=e[i].to;
48 if(d[e[i].to]>d[now]+e[i].w)
49 {
50 d[e[i].to]=d[now]+e[i].w;
51 q.push(make_pair(-d[e[i].to],e[i].to));
52 }
53 }
54 }
55 printf("%d\n",d[n]);
56 }
57 return 0;
58 }
