[JZOJ 5819] 大逃杀

题意：求一个树上背包~~

先贴代码存一下，好像打挂了。

#include <bits/stdc++.h>
using namespace std;
const int maxn = 400;
const int INF = 0x3c;
int dp[maxn][maxn][3];

inline int read() {
	int q=0,f=1;char ch = getchar();
	while(!isdigit(ch)){
		if(ch=='-')f=-1;ch=getchar();
	}
	while(isdigit(ch)){
		q=q*10+ch-'0';ch=getchar();
	}
	return q*f;
}
int cnt;
int head[maxn << 1];
int n,m,t;
struct edge {
	int to;
	int nxt;
	int w;
}e[maxn << 1];
int ans;
inline void Add_edge(int u,int v,int w) {
	e[++cnt].to = v;
	e[cnt].nxt = head[u];
	head[u] = cnt;
	e[cnt].w = w;
	e[++cnt].to = u;
	e[cnt].nxt = head[v];
	head[v] = cnt;
	e[cnt].w = w;
}
int s[maxn];
int cost[maxn];
inline void dfs(int x,int fa) {
	for(int i = 0;i <= t; ++i) {
		if(i < s[x]) {
			dp[x][i][0] = dp[x][i][1] = dp[x][i][2] = -INF;
		}
		else {
			dp[x][i][0] = dp[x][i][1] = dp[x][i][2] = cost[x];
		}
	}
	for(int i = head[x];i;i=e[i].nxt) {
		int y = e[i].to;
		if(y != fa) {
			dfs(y,x);
			for(int j = t;j >= e[i].w; --j) {
				for(int k = 0;k <= j - e[i].w; ++k) {
					if(j - k >= 2 * e[i].w) {
						dp[x][j][2] = max(dp[x][j][2],dp[y][k][0] + dp[x][j - 2 * e[i].w - k][2]);
					}
					if(j - k >= 2 * e[i].w) dp[x][j][2] = max(dp[x][j][2],dp[y][k][2] + dp[x][j - k - 2 * e[i].w][0]);
					dp[x][j][2] = max(dp[x][j][2],dp[y][k][1] + dp[x][j - k - e[i].w][1]);
					if(j - k >= 2 * e[i].w) {
						dp[x][j][1] = max(dp[x][j][1],dp[y][k][0] + dp[x][j - k - 2 * e[i].w][1]);
					}
					dp[x][j][1] = max(dp[x][j][1],dp[y][k][1] + dp[x][j - k - e[i].w][0]);
					if(j - k >= 2 * e[i].w) {
						dp[x][j][0] = max(dp[x][j][0],dp[y][k][0] + dp[x][j - k - 2 * e[i].w][0]);
					}
				}
			}
		}
	}
}
int main () {
	freopen("toyuq.in","r",stdin);
	freopen("toyuq.out","w",stdout);
	n = read(),t = read();
	for(int i = 1;i <= n; ++i) {
		cost[i] = read();
	}
	for(int i = 1;i <= n; ++i) {
		s[i] = read();
	}
	for(int i = 1;i < n; ++i) {
		int x = read(),y = read(),z = read();
		Add_edge(x,y,z);
	}
	dfs(1,0);
	for(int i = 1;i <= n; ++i) {
		ans = max(ans,dp[i][t][2]);
	}
	printf("%d\n",ans);
	return 0;
}