二分答案res,如果權值<=res,爲0,否則爲1,跑dij,如果dis>=k ,則說明res還能再大一點
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int n,m,k;
int edge[10005],cnt;
int g[105][105],vis[105],dis[105];
int mp[105][105];
void dij()
{
memset(vis,0,sizeof(vis));
memset(dis,0x3f3f3f3f,sizeof(dis));
dis[1]=0;
while(1)
{
int p=-1;
for(int i=1; i<=n; i++)
if(!vis[i]&&(p==-1||dis[i]<dis[p]))
p=i;
if(p==-1) return;
vis[p]=1;
for(int i=1; i<=n; i++)
dis[i]=min(dis[i],dis[p]+mp[p][i]);
}
}
int f(int x)
{
for(int i=1; i<=n; i++)
for(int j=1; j<=n; j++)
if(g[i][j]<=x) mp[i][j]=0;
else if(g[i][j]!=0x3f3f3f3f) mp[i][j]=1;
else mp[i][j]=0x3f3f3f3f;
dij();
return dis[n]>=k;
}
int main()
{
// freopen("1.in","r",stdin);
// freopen("1.txt","w+",stdout);
while(~scanf("%d%d%d",&n,&m,&k))
{
k++;
memset(g,0x3f3f3f3f,sizeof(g));
cnt=0;
for(int i=0; i<m; i++)
{
int u,v,w;
scanf("%d%d%d",&u,&v,&w);
if(g[u][v]>w) g[u][v]=g[v][u]=w;
edge[cnt++]=w;
}
for(int i=1; i<=n; i++)
for(int j=1; j<=n; j++)
if(g[i][j]!=0x3f3f3f3f) mp[i][j]=1;
else mp[i][j]=0x3f3f3f3f;
dij();
if(dis[n]==0x3f3f3f3f)
{
puts("-1");
continue;
}
if(dis[n]<k)
{
puts("0");
continue;
}
sort(edge,edge+cnt);
cnt=unique(edge,edge+cnt)-edge;
int l=0,r=cnt-1,mid;
while(l<=r)
{
mid=(l+r)/2;
if(f(edge[mid])) l=mid+1;
else r=mid-1;
}
cout<<edge[l]<<endl;
}
}