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 = 1<<30;

struct Graph {
    static const int MAXN = 111;
    static const int MAXM = MAXN*2;

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

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

    void init(int n, int m) {
        memset(head, -1, sizeof(head));
        use = 0;

        this->m = m;
        for (int i = 1; i <= n; i++) scanf("%d", &val[i]);
        int u, v;
        for (int i = 1; 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], 0, sizeof(dp[u]));
        size[u] = 1;
        for (int p = head[u]; p != -1; p = next[p]) {
            int v = to[p];
            if (v==pre) continue;
            dfs(v, u);
            size[u] += size[v];
        }
        dp[u][1] = val[u];
        for (int p = head[u]; p != -1; p = next[p]) {
            int v = to[p];
            if (v==pre) continue;
            for (int i = size[u]; i > 0; i--)
                for (int j = 1; 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 = 0;
        dfs(1, 1);
        for (int i = 1; i <= m; i++)
            ans = max(ans, dp[1][i]);
        printf("%d
", 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 0;
}