luogu P1315 联合权值 枚举 

 1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 typedef long long ll;
 5 const int N = 200100,M = 400100,mo = 10007;//用变量方便更改 
 6 int cnt,n,maxn;
 7 ll ans;
 8 int w[N],head[N],to[M],nxt[M];
 9 void add(int x,int y)
10 {
11     nxt[++cnt] = head[x];
12     to[cnt] = y;
13     head[x] = cnt;
14 }
15 void dfs(int x,int fa)
16 {
17     ll sum = 0;
18     int max1 = 0,max2 = 0;
19     for (int i = head[x];i;i = nxt[i])
20     {
21         sum += w[to[i]];
22         if (w[to[i]] > max1)//赋值顺序一定要考虑清楚 
23         {
24             max2 = max1;
25             max1 = w[to[i]];
26         }else if (w[to[i]] > max2)//一定要写else，否则？ 
27             max2 = w[to[i]];
28     }
29     maxn = max(maxn,max1 * max2);
30     for (int i = head[x];i;i = nxt[i])
31     {
32         ans += (sum - w[to[i]]) * w[to[i]];
33         ans %= mo;
34     }
35     for (int i = head[x];i;i = nxt[i])
36         if (to[i] != fa)
37             dfs(to[i],x);
38 }
39 int main()
40 {
41     scanf("%d",&n);
42     int u,v;
43     for (int i = 1;i <= n - 1;i++)
44     {
45         scanf("%d%d",&u,&v); 
46         add(u,v);
47         add(v,u);
48     }
49     for (int i = 1;i <= n;i++)
50         scanf("%d",&w[i]);
51     dfs(1,0);
52     printf("%d %lld\n",maxn,ans); 
53     return 0;
54 }

 

posted @ 2019-07-20 17:51  IAT14  阅读(195)  评论(0)  编辑  收藏  举报