89 lines
2.1 KiB
C++
89 lines
2.1 KiB
C++
#include<iostream>
|
|
#include<cstdio>
|
|
#include<queue>
|
|
#include<vector>
|
|
using namespace std;
|
|
const int MAXN=1000+10;
|
|
const int inf=1<<30;
|
|
struct Node{
|
|
int v,w,id;
|
|
};
|
|
vector<Node>vet[MAXN];
|
|
int path[MAXN];
|
|
int dist[MAXN];
|
|
bool visited[MAXN];
|
|
bool mark[MAXN*50];
|
|
int id[MAXN];
|
|
int n,m;
|
|
bool tag;
|
|
void SPFA(int u){
|
|
for(int i=1;i<=n;i++)dist[i]=inf;
|
|
dist[u]=0;
|
|
memset(visited,false,sizeof(visited));
|
|
queue<int>Q;
|
|
Q.push(u);
|
|
while(!Q.empty()){
|
|
int u=Q.front();
|
|
Q.pop();
|
|
visited[u]=false;
|
|
for(int i=0;i<vet[u].size();i++){
|
|
int v=vet[u][i].v;
|
|
int w=vet[u][i].w;
|
|
int ID=vet[u][i].id;
|
|
if(mark[vet[u][i].id])continue;
|
|
if(dist[u]+w<dist[v]){
|
|
dist[v]=dist[u]+w;
|
|
if(tag)path[v]=u,id[v]=ID;
|
|
if(!visited[v]){
|
|
Q.push(v);
|
|
visited[v]=true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
int main(){
|
|
int _case;
|
|
scanf("%d",&_case);
|
|
while(_case--){
|
|
scanf("%d%d",&n,&m);
|
|
for(int i=1;i<=n;i++)vet[i].clear();
|
|
memset(path,-1,sizeof(path));
|
|
memset(mark,false,sizeof(mark));
|
|
for(int i=1;i<=m;i++){
|
|
int u,v,w;
|
|
scanf("%d%d%d",&u,&v,&w);
|
|
Node p1,p2;
|
|
p1.v=u,p2.v=v;
|
|
p1.w=p2.w=w;
|
|
p1.id=p2.id=i;
|
|
vet[u].push_back(p2);
|
|
vet[v].push_back(p1);
|
|
}
|
|
tag=true;
|
|
SPFA(1);
|
|
tag=false;
|
|
if(dist[n]==inf){
|
|
printf("-1\n");
|
|
continue;
|
|
}
|
|
int ans=0;
|
|
bool flag=true;
|
|
for(int u=n;u!=-1;u=path[u]){
|
|
mark[id[u]]=true;
|
|
SPFA(1);
|
|
mark[id[u]]=false;
|
|
if(dist[n]==inf){
|
|
printf("-1\n");
|
|
flag=false;
|
|
break;
|
|
}
|
|
ans=max(ans,dist[n]);
|
|
}
|
|
if(flag){
|
|
printf("%d\n",ans);
|
|
}
|
|
}
|
|
return 0;
|
|
}
|