caioj 1114 树形动态规划（TreeDP）3.0：多叉苹果树【scy改编ural1018二叉苹果树】

一波树上背包秒杀……

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;

const int MAXN = 312;
int f[MAXN][MAXN], cnt[MAXN], n, k;
struct node{ int v, w; };
vector<node> g[MAXN];

void dfs(int u, int fa)
{
	REP(i, 0, g[u].size())
	{
		int v = g[u][i].v, w = g[u][i].w;
		if(v == fa) continue;
		dfs(v, u);
		cnt[u] += cnt[v];
		for(int j = cnt[u]; j >= 1; j--)
			REP(k, 1, min(cnt[v], j - 1) + 1)
				f[u][j] = max(f[u][j], f[u][j-k] + f[v][k] + w);
	}
}

int main()
{
	scanf("%d%d", &n, &k);
	REP(i, 1, n)
	{
		int u, v, w;
		scanf("%d%d%d", &u, &v, &w);
		g[u].push_back(node{v, w});
		g[v].push_back(node{u, w});
		cnt[i] = 1;
	}
	cnt[n] = 1;
	
	dfs(1, -1);
	printf("%d
", f[1][k + 1]);
	
	return 0;
}