bzoj 2662

 1 #include<bits/stdc++.h>
 2 #define inc(i,l,r) for(i=l;i<=r;i++)
 3 #define dec(i,l,r) for(i=l;i>=r;i--)
 4 #define inf 1e9
 5 #define mem(a) memset(a,0,sizeof(a))
 6 #define ll long long
 7 #define NM 50+5
 8 using namespace std;
 9 int read(){
10     int x=0,f=1;char ch=getchar();
11     while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
12     while(isdigit(ch))x=x*10+ch-‘0‘,ch=getchar();
13     return f*x;
14 }
15 struct edge{
16     int t,v;
17     edge *next;
18 }e[2005],*h[NM];
19 queue<int >q;
20 int d[NM][NM],n,m,p,i,x,y,t,s,ans;
21 bool v[NM];
22 void add(int x,int y,int v){
23     e[++s].t=y;e[s].v=v;e[s].next=h[x];h[x]=&e[s];
24 }
25 int spfa(){
26     ans=inf;
27     inc(i,0,p){
28         mem(v);
29         v[1]++;q.push(1);d[i][1]++;
30         while(!q.empty()){
31             int t=q.front();q.pop();v[t]=false;
32             for(edge *j=h[t];j;j=j->next){
33                 if(!d[i][j->t]||d[i][j->t]>d[i][t]+j->v){
34                     d[i][j->t]=d[i][t]+j->v;
35                     if(!v[j->t]){
36                         v[j->t]++;q.push(j->t);
37                     }
38                 }
39                 if(i>0)
40                 if(!d[i][j->t]||d[i][j->t]>d[i-1][t]+j->v/2){
41                     d[i][j->t]=d[i-1][t]+j->v/2;
42                     if(!v[j->t]){
43                         v[j->t]++;q.push(j->t);
44                     }
45                 }
46             }
47         }
48         ans=min(ans,d[i][n]-1);
49     }
50     return ans;
51 }
52 int main(){
53     n=read();m=read();p=read();
54     inc(i,1,m){
55         x=read();y=read();t=read();
56         add(x,y,t);add(y,x,t);
57     }
58     printf("%d",spfa());
59     return 0;
60 }