AC代码
#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
#define inf 0x3f3f3f3f
int book[1010],dist[1010],e[1010][1010],pre[1010];
int n,m;
bool flag;
void dijkstra()
{
for(int i=1; i<=n; i++)
{
//dist[i]=e[1][i];
dist[i]=inf;
book[i]=0;
}
//book[1]=1;
dist[1]=0;
int u;
for(int i=2; i<=n; i++)
{
int minn=inf;
for(int j=1; j<=n; j++)
{
if(book[j]==0&&minn>dist[j])
{
u=j;
minn=dist[j];
}
}
if(minn==inf)
break;
book[u]=1;
for(int j=1; j<=n; j++)
{
if(book[j]==0&&e[u][j]<inf)
{
if(dist[u]+e[u][j]<dist[j])
{
dist[j]=dist[u]+e[u][j];
if(flag==0)
pre[j]=u;
}
}
}
}
}
int main()
{
while(cin>>n>>m)
{
for(int i=1; i<=n; i++)
{
pre[i]=-1;
for(int j=1; j<=n; j++)
{
if(i==j)
e[i][j]=0;
else
e[i][j]=inf;
}
}
for(int i=1; i<=m; i++)
{
int a,b,c;
cin>>a>>b>>c;
e[a][b]=e[b][a]=min(e[a][b],c);
}
flag=0,dijkstra();
flag=1;
int x=dist[n];
// pre[1]=1;
for(int i=n; i!=-1; i=pre[i])
{
int t=e[i][pre[i]];
e[i][pre[i]]=e[pre[i]][i]=inf;
dijkstra();
if(dist[n]!=inf)
x=max(x,dist[n]);
e[i][pre[i]]=e[pre[i]][i]=t;
}
cout<<x<<endl;
}
return 0;
}