UVa 1407 树形背包 Caves

这道题可以和POJ 2486 树形背包DP Apple Tree比较着来做。

参考题解

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <vector>
 6 using namespace std;
 7
 8 const int maxn = 500 + 10;
 9
10 int n, Q;
11 vector<int> G[maxn], C[maxn];
12
13 int d[maxn][maxn][2], cnt[maxn];
14
15 void dfs(int u)
16 {
17     cnt[u] = 1;
18     d[u][1][0] = d[u][1][1] = 0;
19     for(int i = 0; i < G[u].size(); i++)
20     {
21         int v = G[u][i];
22         int w = C[u][i];
23         dfs(v);
24         cnt[u] += cnt[v];
25
26         for(int j = cnt[u]; j >= 2; j--)
27             for(int x = 0; x <= j && x <= cnt[v]; x++)
28             {
29                 d[u][j][0] = min(d[u][j][0], d[v][x][0] + d[u][j-x][0] + w * 2);
30                 d[u][j][1] = min(d[u][j][1], d[v][x][0] + d[u][j-x][1] + w * 2);
31                 d[u][j][1] = min(d[u][j][1], d[v][x][1] + d[u][j-x][0] + w);
32             }
33     }
34 }
35
36 int main()
37 {
38     int kase = 1;
39     while(scanf("%d", &n) == 1 && n)
40     {
41         for(int i = 0; i < n; i++) { G[i].clear(); C[i].clear(); }
42         for(int i = 1; i < n; i++)
43         {
44             int a, b, d; scanf("%d%d%d", &a, &b, &d);
45             G[b].push_back(a); C[b].push_back(d);
46         }
47
48         memset(d, 0x3f, sizeof(d));
49         dfs(0);
50
51         printf("Case %d:\n", kase++);
52         scanf("%d", &Q);
53         while(Q--)
54         {
55             int x; scanf("%d", &x);
56             int ans;
57             for(ans = n; ans > 0; ans--) if(d[0][ans][1] <= x) break;
58             printf("%d\n", ans);
59         }
60     }
61
62     return 0;
63 }

代码君