1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <vector>
 5 #include <algorithm>
 6 using namespace std;
 7
 8 const int maxn = 10000 + 10;
 9 const int maxk = 12;
10
11 int n, s, k;
12
13 vector<int> G[maxn], C[maxn];
14
15 int f[maxn][maxk];
16
17 void DP(int u, int fa)
18 {
19     for(int i = 0; i < G[u].size(); i++)
20     {
21         int v = G[u][i], w = C[u][i];
22         if(v == fa) continue;
23         DP(v, u);
24         for(int i = k; i >= 1; i--)
25             for(int j = 1; j <= i; j++)
26                 f[u][i] = max(f[u][i], f[u][i-j] + f[v][j] + (2 - j) * w);
27     }
28 }
29
30 int main()
31 {
32     while(scanf("%d%d%d", &n, &s, &k) == 3)
33     {
34         for(int i = 1; i <= n; i++) { G[i].clear(); C[i].clear(); }
35
36         int sum = 0;
37         for(int i = 1; i < n; i++)
38         {
39             int u, v, w; scanf("%d%d%d", &u, &v, &w);
40             sum += w;
41             G[u].push_back(v); C[u].push_back(w);
42             G[v].push_back(u); C[v].push_back(w);
43         }
44         sum <<= 1;
45
46         memset(f, 0, sizeof(f));
47         DP(s, 0);
48         printf("%d\n", sum - f[s][k]);
49     }
50
51     return 0;
52 }

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 #include <cstring>
 5 #include <vector>
 6 using namespace std;
 7
 8 const int maxn = 10000 + 10;
 9
10 struct Edge
11 {
12     int u, v, w;
13     Edge(int u, int v, int w):u(u), v(v), w(w) {}
14 };
15
16 vector<Edge> edges;
17 vector<int> G[maxn];
18
19 void AddEdge(int u, int v, int w)
20 {
21     edges.push_back(Edge(u, v, w));
22     edges.push_back(Edge(v, u, w));
23     int m = edges.size();
24     G[u].push_back(m - 2);
25     G[v].push_back(m - 1);
26 }
27
28 int n, s, k;
29
30 int len, id;
31 int pre[maxn];
32
33 void dfs(int u, int fa, int d)
34 {
35     if(d > len) { len = d; id = u; }
36     for(int i = 0; i < G[u].size(); i++)
37     {
38         Edge& e = edges[G[u][i]];
39         int v = e.v;
40         if(v == fa) continue;
41         pre[v] = G[u][i];
42         dfs(v, u, d + e.w);
43     }
44 }
45
46 int main()
47 {
48     while(scanf("%d%d%d", &n, &s, &k) == 3)
49     {
50         edges.clear();
51         int tot = 0;
52         for(int i = 1; i <= n; i++) G[i].clear();
53         for(int i = 1; i < n; i++)
54         {
55             int u, v, w; scanf("%d%d%d", &u, &v, &w);
56             tot += w;
57             AddEdge(u, v, w);
58         }
59         tot <<= 1;
60
61         int ans = 0;
62         for(int i = 0; i < k; i++)
63         {
64             len = 0, id = s;
65             pre[s] = -1;
66             dfs(s, 0, 0);
67             if(id == s) continue;
68             ans += len;
69             for(int u = id; u != s; u = edges[pre[u]].u)
70             {
71                 int& w = edges[pre[u]].w;
72                 if(w > 0) w = -w;
73             }
74         }
75
76         printf("%d\n", tot - ans);
77     }
78
79     return 0;
80 }