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lightoj 1099.cpp
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lightoj 1099.cpp
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#include<bits/stdc++.h>
using namespace std;
#define mx 5005
#define ll long long
#define inf 1e9
void IO()
{
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
}
vector<pair<int,int>>g[mx];
int dis[mx][2],vis[mx];
int m,n,k,ii,re;
void bfs(int u)
{
priority_queue<pair<int,int>>q;
dis[u][k]=0;
q.push({0,u});
while(!q.empty())
{
u=q.top().second;
int val=q.top().first;
val*=-1;
q.pop();
if(dis[u][k]<val)continue;
for(auto it:g[u])
{
int val1=val+it.second;
int v=it.first;
if(val1<dis[v][k])
{
dis[v][k]=val1;
q.push({-val1,v});
}
}
}
}
void dfs(int u)
{
vis[u]=1;
for(auto it:g[u])
{
int v=it.first;
//cout<<u<<" "<<v<<endl;
if(dis[u][0]+dis[v][1]+it.second!=dis[n][0])
{
re=min(re,dis[u][0]+dis[v][1]+it.second);
}
else
re=min(re,dis[u][0]+dis[v][1]+it.second*3);
if(dis[u][1]+dis[v][0]+it.second!=dis[n][0])
{
re=min(re,dis[u][1]+dis[v][0]+it.second);
}
else
re=min(re,dis[u][1]+dis[v][0]+it.second*3);
if(u!=n && u!=1)
re=min(re,dis[n][0]+dis[u][0]*2);//,cout<<u<<" "<<dis[u][0]<<endl;
if(v!=n && v!=1)
re=min(re,dis[n][0]+dis[v][0]*2);//,cout<<v<<" "<<dis[v][0]<<endl;
if(vis[v]==1)continue;
dfs(v);
}
}
void solve()
{
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++)
{
int x,y,w;
scanf("%d%d%d",&x,&y,&w);
g[x].push_back({y,w});
g[y].push_back({x,w});
}
for(int i=1;i<=n;i++)dis[i][0]=dis[i][1]=inf,vis[i]=0;
k=0;
bfs(1);
k=1;
bfs(n);
re=inf;
dfs(1);
// for(int i=1;i<=n;i++)printf("%d %d\n",dis[i][0],dis[i][1] );
printf("Case %d: %d\n",++ii,re);
for(int i=1;i<=n;i++)g[i].clear();
}
int main()
{
IO();
int t=1;
scanf("%d",&t);
while(t--)
{
solve();
}
return 0;
}