OJ-Problems-Source/HDOJ/3986_autoAC.cpp
2016-09-04 14:19:03 +08:00

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;
}