hdu 1011 树形背包

很显然是树形背包，注意m为0的情况。

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 using namespace std;
 5 
 6 const int N = 101;
 7 int head[N];
 8 int bn[N];
 9 int value[N];
10 int dp[N][N];
11 int n, m, e;
12 
13 struct Edge 
14 {
15     int v, next;
16 } edge[N << 1];
17 
18 void addEdge( int u, int v )
19 {
20     edge[e].v = v;
21     edge[e].next = head[u];
22     head[u] = e++;
23 }
24 
25 void dfs( int u, int fa )
26 {
27     int tmp = ( bn[u] + 19 ) / 20;
28     for ( int i = tmp; i <= m; i++ ) dp[u][i] = value[u];
29     for ( int i = head[u]; i != -1; i = edge[i].next )
30     {
31         int v = edge[i].v;
32         if ( v == fa ) continue;
33         dfs( v, u );
34         for ( int j = m; j >= tmp; j-- )
35         {
36             for ( int k = 1; j - k >= tmp; k++ )
37             {
38                 dp[u][j] = max( dp[u][j], dp[u][j - k] + dp[v][k] );
39             }
40         }
41     }
42 }
43 
44 int main ()
45 {
46     while ( scanf("%d%d", &n, &m) != EOF )
47     {
48         if ( n == -1 && m == -1 ) break;
49         for ( int i = 1; i <= n; i++ )
50         {
51             scanf("%d%d", bn + i, value + i);
52         }
53         e = 0;
54         memset( head, -1, sizeof(head) );
55         for ( int i = 1; i < n; i++ )
56         {
57             int u, v;
58             scanf("%d%d", &u, &v);
59             addEdge( u, v );
60             addEdge( v, u );
61         }
62         if ( !m )
63         {
64             puts("0");
65             continue;
66         }
67         memset( dp, 0, sizeof(dp) );
68         dfs( 1, -1 );
69         printf("%d\n", dp[1][m]);
70     }
71     return 0;
72 }

 

posted @ 2015-08-11 09:49  hxy_has_been_used  阅读(149)  评论(0)  编辑  收藏  举报