1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
|
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<iostream>
#include<queue>
using namespace std;
const int maxn=20005;
typedef pair<int,int> p;
int n,m,k;
int vis[maxn],dis[maxn];
int num=0,head[maxn];
inline int read()
{
int x=0,t=1;char ch=getchar();
while(ch>'9'||ch<'0'){if(ch=='-')t=-1;ch=getchar();}
while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
return x*t;
}
struct node{
int v,w,nex;
}e[maxn];
void add(int u,int v,int w)
{
e[++num].v=v;
e[num].w=w;
e[num].nex=head[u];
head[u]=num;
}
int check(int x)
{
priority_queue<p,vector<p>,greater<p> >q;
memset(vis,0,sizeof(vis));
memset(dis,0x3f,sizeof(dis));
dis[1]=0;
q.push(make_pair(0,1));
while(!q.empty())
{
int u=q.top().second;
q.pop();
if(vis[u]) continue;
vis[u]=1;
for(int i=head[u];i;i=e[i].nex)
{
int v=e[i].v;
if(dis[v]>dis[u]+(e[i].w-x>0?1:0))
{
dis[v]=dis[u]+(e[i].w-x>0?1:0);
q.push(make_pair(dis[v],v));
}
}
}
return dis[n]<=k;
}
int main()
{
n=read(),m=read(),k=read();
for(int i=1;i<=m;i++)
{
int x,y,z;
x=read(),y=read(),z=read();
add(x,y,z);
add(y,x,z);
}
int l=0,r=1000002;
while(l<r)
{
int mid=(l+r)>>1;
if(check(mid)) r=mid;
else l=mid+1;
}
if(l>1000000) printf("-1\n");
else printf("%d\n",l);
return 0;
}
|