hdu 1011 Starship Troopers

http://acm.hdu.edu.cn/showproblem.php?pid=1011

　　入门级树dp，这题就是要注意一下输入的时候要特判一个m为0的情况。

View Code

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <vector>
 6 #include <algorithm>
 7 
 8 using namespace std;
 9 
10 const int maxn = 105;
11 
12 int dp[maxn][maxn];
13 bool vis[maxn];
14 int p[maxn], b[maxn];
15 vector<int> nd[maxn];
16 
17 int max2(int x, int y){return (x > y) ? x : y;}
18 
19 void init(int n, int m){
20     for (int i = 1; i <= n; i++){
21         vis[i] = false;
22         p[i] = b[i] = 0;
23         nd[i].clear();
24     }
25     memset(dp, 0, sizeof(dp));
26 }
27 
28 bool data(int &n, int &m){
29     scanf("%d%d", &n, &m);
30     if (n == -1 && m == -1) return false;
31     init(n, m);
32     for (int i = 1; i <= n; i++){
33         scanf("%d%d", &b[i], &p[i]);
34     }
35     for (int i = 1, x, y; i < n; i++){
36         scanf("%d%d", &x, &y);
37         nd[x].push_back(y);
38         nd[y].push_back(x);
39     }
40     return true;
41 }
42 
43 void dfs(int m, int rt){
44     vis[rt] = true;
45     int bg = (b[rt] + 19) / 20;
46 
47     for (int i = bg; i <= m; i++)
48         dp[rt][i] = p[rt];
49     if (bg <= m && !nd[rt].size()){
50         return ;
51     }
52     for (int i = 0; i < nd[rt].size(); i++){
53         if (vis[nd[rt][i]]) continue;
54         dfs(m, nd[rt][i]);
55         for (int j = m; j >= bg; j--){
56             for (int k = 1; k <= j - bg; k++){
57                 dp[rt][j] = max2(dp[rt][j - k] + dp[nd[rt][i]][k], dp[rt][j]);
58             }
59         }
60     }
61 }
62 
63 int main(){
64     int n, m;
65 
66     while (true){
67         if (!data(n, m)) return 0;
68         if (!m){
69             printf("0\n");
70             continue;
71         }
72         dfs(m, 1);
73         printf("%d\n", dp[1][m]);
74     }
75 }

——written by Lyon

posted @ 2012-08-17 17:08 LyonLys 阅读(158) 评论(0) 收藏举报

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