ZOJ 3626 Treasure Hunt I / 树形DP

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

const int maxn = 110;

struct node
{
	int e;
	int w;
};
int dp[maxn][maxn*2];
vector <node> a[maxn];
int b[maxn];
bool vis[maxn];
int n, s, m;

void dfs(int u, int t)
{
	//if(vis[u][t])
	//	return dp[u][t];
	if(t < 0)
		return;
	for(int i = 0; i <= t; i++)
		dp[u][i] = b[u];
	vis[u] = true;
	for(int i = 0; i < a[u].size(); i++)
	{
		node v = a[u][i];
		if(vis[v.e])
			continue;
		dfs(v.e, t-2*v.w);
		for(int j = t; j >= 2*v.w; j--)
		{
			for(int k = 0; k <= j-2*v.w; k++)
			{
				node vv = a[v.e][i];
				dp[u][j] = max(dp[u][j], dp[u][j-k-2*v.w] + dp[v.e][k]);
			}
		}
	}
}
int main()
{
	while(scanf("%d", &n) == 1)
	{
		for(int i = 1; i <= n; i++)
		{
			scanf("%d", &b[i]);
			a[i].clear();
		}
		for(int i = 1; i < n; i++)
		{
			int u, v, w;
			scanf("%d %d %d", &u, &v, &w);
			a[u].push_back((node){v, w});
			a[v].push_back((node){u, w});
		}
		scanf("%d %d", &s, &m);
		memset(dp, 0, sizeof(dp));
		memset(vis, false, sizeof(vis));
		dfs(s, m);
		printf("%d\n", dp[s][m]);
	}
	return 0;
}