hdu1520

基本的树形dp

#include <cstring>
#include <cstdio>
#include <vector>
using namespace std;

const int MAX_N = (int)(6e3) + 5;

int n;
int weight[MAX_N];
vector <int> edge[MAX_N];
bool vis[MAX_N];
int dp[MAX_N][2];
int root;

void dfs(int father, int u)
{
    for (int i = 0; i < (int)edge[u].size(); i++)
    {
        int v = edge[u][i];
        if (v != father)
            dfs(u, v);
    }
    dp[u][0] = 0;
    dp[u][1] = weight[u];
    for (int i = 0; i < (int)edge[u].size(); i++)
    {
        int v = edge[u][i];
        if (v == father)
            continue;
        dp[u][0] += max(dp[v][0], dp[v][1]);
        dp[u][1] += dp[v][0];
    }
}

void input()
{
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &weight[i]);
        edge[i].clear();
    }
    memset(vis, 0, sizeof(vis));
    int a, b;
    while (scanf("%d%d", &a, &b), a | b)
    {
        a--;
        b--;
        vis[a] = true;
        edge[a].push_back(b);
        edge[b].push_back(a);
    }
    for (int i = 0; i < n; i++)
    {
        if (!vis[i])
        {
            root = i;
            break;
        }
    }
}

int main()
{
    while (scanf("%d", &n) != EOF)
    {
        input();
        dfs(-1, root);
        printf("%d\n", max(dp[root][0], dp[root][1]));
    }
    return 0;
}