hiho 1055 刷油漆 树形dp

一个简单的树上的背包问题。

代码：

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <cmath>
 #include <algorithm>
 #include <string>
 #include <queue>
 #include <stack>
 #include <vector>
 #include <map>
 #include <set>
 #include <functional>
 #include <cctype>
 #include <time.h>

 using namespace std;

 const int INF = <<;

 struct Graph {
     static const int MAXN = ;
     static const int MAXM = MAXN*;

     int head[MAXN];
     int next[MAXM], to[MAXM], use;

     int val[MAXN], size[MAXN];
     int m;

     void init(int n, int m) {
         memset(head, -, sizeof(head));
         use = ;

         this->m = m;
         for (int i = ; i <= n; i++) scanf("%d", &val[i]);
         int u, v;
         for (int i = ; i < n; i++) {
             scanf("%d%d", &u, &v);
             addEdge(u, v);
             addEdge(v, u);
         }
     }

     inline void addEdge(int u, int v) {
         next[use] = head[u];
         to[use] = v;
         head[u] = use++;
     }

     int dp[MAXN][MAXN];

     void dfs(int u, int pre) {
         memset(dp[u], , sizeof(dp[u]));
         size[u] = ;
         for (int p = head[u]; p != -; p = next[p]) {
             int v = to[p];
             if (v==pre) continue;
             dfs(v, u);
             size[u] += size[v];
         }
         dp[u][] = val[u];
         for (int p = head[u]; p != -; p = next[p]) {
             int v = to[p];
             if (v==pre) continue;
             for (int i = size[u]; i > ; i--)
                 for (int j = ; j <= size[v]; j++) {
                     if (i+j>size[u]) break;
                     dp[u][i+j] = max(dp[u][i+j], dp[u][i]+dp[v][j]);
                 }
         }
     }

     void solve() {
         int ans = ;
         dfs(, );
         for (int i = ; i <= m; i++)
             ans = max(ans, dp[][i]);
         printf("%d\n", ans);
     }
 }solver;

 int main() {
     #ifdef Phantom01
         freopen("1055.txt", "r", stdin);
     #endif //Phantom01

     int n, m;
     while (scanf("%d%d", &n, &m)!=EOF) {
         solver.init(n, m);
         solver.solve();
     }

     return ;
 }