bzoj 1614 Telephone Lines

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <queue>
 4 #include <cstring>
 5 
 6 
 7 struct node{
 8     int u,v,w,next;
 9     node(){}
10     node(int _u,int _v,int _w,int _next){
11         u = _u;
12         v = _v;
13         w = _w;
14         next = _next;
15     }
16 }Edge[20005];
17 
18 int n,p,k,Count,head[10005];
19 int x,y,z,dis[1005],ans=-1;
20 bool inque[1005];
21 
22 void AddEdge(int u,int v,int w){
23     Count++;
24     Edge[Count]=node(u,v,w,head[u]);
25     head[u]=Count;
26 }
27 
28 bool spfa(int x){
29     memset(dis,0x3f3f3f3f,sizeof(dis));
30     memset(inque,0,sizeof(inque));
31     std::queue<int>Q;
32     Q.push(1);
33     int s;
34     inque[1]=1;
35     dis[1]=0;
36     while( !Q.empty() ){
37         int now = Q.front();
38         Q.pop();
39         inque[now]=0;
40         for(int i=head[now];i;i=Edge[i].next){
41             if(Edge[i].w>x) s=dis[now]+1;
42             else s = dis[now];
43             if(s<dis[Edge[i].v]){
44                 dis[Edge[i].v] = s;
45                 if(!inque[Edge[i].v]){
46                     Q.push(Edge[i].v);
47                     inque[Edge[i].v]=1;
48                 }
49             }
50         }
51     }
52     //printf("%d\n",dis[n]);
53     if(dis[n]<=k) return true;
54     return false;
55 }
56 
57 int main(){
58     scanf("%d%d%d",&n,&p,&k);
59     for(int i=1;i<=p;i++){
60         scanf("%d%d%d",&x,&y,&z);
61         AddEdge(x,y,z);
62         AddEdge(y,x,z);
63     }
64     int l = 0,r = 1000000;
65     while(l<=r){
66         int mid = (l+r)>>1;
67         if( spfa(mid) ){
68             ans = mid;
69             r = mid - 1;
70         }
71         else l = mid + 1;
72     }
73     printf("%d\n",ans);
74     return 0;
75 }