【HDOJ】1011 Starship Troopers

第一道树形DP。很容易理解。

#include <cstdio>
#include <cstring>
#include <cstdlib>

#define MAXN 105

typedef struct {
    int n, p;
} room_t;

room_t rooms[MAXN];
int adj[MAXN][MAXN];
int dp[MAXN][MAXN];
bool visit[MAXN];
int n, m;

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

void dfs(int r) {
    int i, j, k, num, v;
    
    visit[r] = true;
    num = (rooms[r].n+19) / 20;
    for (i=num; i<=m; ++i)
        dp[r][i] = rooms[r].p;
        
    for (i=1; i<=adj[r][0]; ++i) {
        v = adj[r][i];
        if (visit[v])
            continue;
        dfs(v);
        for (j=m; j>=num; --j) {
            for (k=1; k+j<=m; ++k) {
                if (dp[v][k]) {
                    dp[r][j+k] = max(dp[r][j+k], dp[r][j]+dp[v][k]);
                }
            }
        }
    }
}

int main() {
    int i, j, k;
    
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif

    while (scanf("%d %d", &n, &m) != EOF) {
        if (n==-1 && m==-1)
            break;
        memset(adj, 0, sizeof(adj));
        memset(visit, false, sizeof(visit));
        memset(dp, 0, sizeof(dp));
        for (i=1; i<=n; ++i) {
            scanf("%d %d", &rooms[i].n, &rooms[i].p);
        }
        for (i=1; i<n; ++i) {
            scanf("%d %d", &j, &k);
            ++adj[j][0];
            ++adj[k][0];
            adj[j][adj[j][0]] = k;
            adj[k][adj[k][0]] = j;
        }
        if (m == 0) {
            printf("0\n");
            continue;
        }
        dfs(1);
        printf("%d\n", dp[1][m]);
    }

    return 0;
}