# HDU 4479 Shortest path(最短路)

3
5 5
1 2 1
2 3 2
3 4 3
1 4 4
4 5 4
5 5
1 2 2
2 3 3
3 4 4
1 4 5
4 5 5
5 5
1 2 2
2 3 3
3 4 4
1 4 5
4 5 6

```#include <cstdio>
#include <queue>
#include <cstring>
#include <algorithm>
#include <stack>
#include <iostream>
using namespace std;
#define LL long long
const int N = 10009;
const int M = 100009;
const LL INF = 0x3f3f3f3f3f3f3f3f;
int f,t,dis;
bool operator<(const load t)const{
return dis<t.dis;
}
} ld[M];
int n,m;
int fa[N];
LL dis[N];
int v[N];
LL vdis[N];
void oper(int st,int len)
{
int cnt=  0,l,r,d;
for(int i=0;i<len;i++)
{
l = ld[i+st].f,r= ld[st+i].t,d = ld[st+i].dis;
if(fa[l]&&dis[r]>d+dis[l])
{
v[cnt] = r;
vdis[cnt]= d+dis[l];
cnt++;
}
if(fa[r]&&dis[l]>d+dis[r])
{
v[cnt] = l;
vdis[cnt] = d+dis[r];
cnt++;
}
}
for(int i=0;i<cnt;i++)
{
dis[v[i]] = min(dis[v[i]],vdis[i]);
fa[v[i]] = 1;
}
}
void solve()
{
memset(fa,0,sizeof(fa));
for(int i=0;i<=n;i++) dis[i] = INF;
dis[1] = 0;
fa[1] = 1;
for(int i=0;i<m;)
{
int j;
for(j=i+1;j<m;j++)
{
if(ld[j].dis!=ld[i].dis) break;
}
oper(i,j-i);
i = j;
}
if(dis[n]!=INF)
cout<<dis[n]<<endl;
}
int main()
{
freopen("in.txt","r",stdin);
int cas;
scanf("%d",&cas);
while(cas--)
{
scanf("%d%d",&n,&m);
for(int i=0;i<m;i++)
scanf("%d%d%d",&ld[i].f,&ld[i].t,&ld[i].dis);
sort(ld,ld+m);
solve();
}
return 0;
}
```