1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 
 5 using namespace std;
 6 
 7 struct Edge{
 8 int to;
 9 int value;
10 int next;
11 }edge[2*10008];
12 int head[10008],dp[10008][12];
13 int N,S,K,total;
14 
15 inline int MIN(int a,int b)
16 {
17     if(a<b) return a;
18     return b;
19 }
20 void addEdge(int start,int end,int value)
21 {
22     edge[total].to=end;edge[total].value=value;
23     edge[total].next=head[start];head[start]=total++;
24 
25     edge[total].to=start,edge[total].value=value;
26     edge[total].next=head[end],head[end]=total++;
27 }
28 
29 void DP(int source,int pre)
30 {
31     for(int i=head[source];i!=-1;i=edge[i].next)
32     {
33         int to=edge[i].to;
34         if(to==pre) continue;
35         DP(to,source);
36         for(int j=K;j>=0;j--)
37         {
38             dp[source][j]+=dp[to][0]+2*edge[i].value;
39             for(int k=1;k<=j;k++)
40                 dp[source][j]=MIN(dp[source][j],dp[source][j-k]+dp[to][k]+k*edge[i].value);
41         }
42     }
43 }
44 
45 int main()
46 {
47    while(scanf("%d %d %d",&N,&S,&K)!=EOF)
48    {
49        memset(dp,0,sizeof(dp));
50        memset(head,-1,sizeof(head));
51        total=0;
52 
53        int x,y,cost;
54        for(int i=1;i<N;i++)
55        {
56            scanf("%d %d %d",&x,&y,&cost);
57            addEdge(x,y,cost);
58        }
59        DP(S,-1);
60        printf("%d\n",dp[S][K]);
61    }
62     return 0;
63 }

 1 void DP(int source,int pre)
 2 {
 3     for(int i=head[source];i!=-1;i=edge[i].next)
 4     {
 5         int to=edge[i].to;
 6         if(to==pre) continue;
 7         DP(to,source);
 8         for(int j=K;j>=0;j--)
 9         {
10             dp[source][j]+=dp[to][0]+2*edge[i].value;
11             for(int k=1;k<=j;k++)
12                 dp[source][j]=MIN(dp[source][j],dp[source][j-k]+dp[to][k]+k*edge[i].value);
13         }
14     }
15 }