hihocoder1779 公路收费

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const ll INF = 0x3f3f3f3f3f3f3f3f;
 5 ll a[1005], cnt[1005], buf[2005];
 6 int n, k;
 7 struct edge
 8 {
 9     int id, to; ll cost;
10     edge(int id, int to, ll cost): id(id), to(to), cost(cost) {}
11 };
12 vector<edge> G[1005];
13 void dfs(int u, int f)
14 {
15     for (int i = 0; i < G[u].size(); i++)
16     {
17         int id = G[u][i].id, v = G[u][i].to; ll c = G[u][i].cost;
18         if (v == f) continue;
19         dfs(v, u);
20         cnt[u] += cnt[v];
21         buf[id] = cnt[v] * c;
22     }
23     cnt[u] += a[u];
24 }
25 bool cmp(ll a, ll b)
26 {
27     return a > b;
28 }
29 int main()
30 {
31     cin >> n >> k;
32     for (int i = 1; i <= n; i++) cin >> a[i];
33     int x, y; ll w;
34     for (int i = 0; i < n - 1; i++)
35     {
36         cin >> x >> y >> w;
37         edge e(i, y, w);
38         G[x].push_back(e);
39         edge e1(i + n - 1, x, w);
40         G[y].push_back(e1);
41     }
42     ll ans = INF;
43     for (int i = 1; i <= n; i++)
44     {
45         memset(buf, 0, sizeof buf);
46         memset(cnt, 0, sizeof cnt);
47         dfs(i, 0);
48         sort(buf, buf + 2 * n - 2, cmp);
49         ll tmp = 0;
50         for (int i = 0; i < 2 * n - 2; i++)
51         {
52             if (i < k) continue;
53             tmp += buf[i];
54         }
55         ans = min(ans, tmp);
56     }
57     cout << ans << endl;
58     return 0;
59 }