HDU 1011 Starship Troopers(树形背包）

Starship Troopers

#include <iostream>
#include <vector>
#include <cstring>
#include <cstdio>
using namespace std;
const int maxn = 110;
int n, m;
int cos[maxn], weg[maxn];
int dp[maxn][maxn];
bool vis[maxn];
vector<int> tree[maxn];//建树

inline int max(int a, int b) {
    return a > b ? a : b;
}

void dfs(int p) {
    int i, j, k;
    int temp = (cos[p] + 19)/20;//攻打p至少需要temp个人
    for(i = temp; i <= m; i++)
        dp[p][i] = weg[p];

    vis[p] = 1;//记录下已经处理p节点,强制只能顺着树往下撸
    for(i = 0; i < tree[p].size(); i++) {
        int t = tree[p][i];
        if(vis[t])
            continue;

        dfs(t);
        for(j = m; j >= temp; j--) {//树形背包,容量从后向前推
            for(k = 1; k <= j-temp; k++)//留下j-k攻打p,k攻打儿子
                dp[p][j] = max(dp[p][j], dp[p][j-k] + dp[t][k]);
        }
    }
}

int main() {
    freopen("data.in", "r", stdin);
    int i;
    while(scanf("%d%d", &n, &m), n != -1 || m != -1) {
        for(i = 0; i <= n; i++)
            tree[i].clear();

        memset(dp, 0, sizeof(dp));
        memset(vis, 0, sizeof(vis));

        for(i = 1; i <= n; i++)
            scanf("%d%d", cos+i, weg+i);

        for(i = 1; i < n; i++) {
            int u, v;
            scanf("%d%d", &u, &v);
            tree[u].push_back(v);
            tree[v].push_back(u);
        }

        if(m == 0) {
            printf("0\n");
            continue;
        }

        dfs(1);
        printf("%d\n", dp[1][m]);
    }

    return 0;
}