[luoguP2015] 二叉苹果树（DP）

传送门

 

貌似是个树形背包。。。

好像吧。。

f[i][j]表示节点i选条边的最优解

 

#include <cstdio>
#include <cstring>
#include <iostream>
#define N 101
#define max(x, y) ((x) > (y) ? (x) : (y))

int n, q, cnt;
int head[N], to[N << 1], next[N << 1], val[N << 1], f[N][N];
bool vis[N];

inline int read()
{
	int x = 0, f = 1;
	char ch = getchar();
	for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;
	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';
	return x * f;
}

inline void add(int x, int y, int z)
{
	to[cnt] = y;
	val[cnt] = z;
	next[cnt] = head[x];
	head[x] = cnt++;
}

inline void dfs(int u)
{
	int i, j, k, v;
	vis[u] = 1;
	for(i = head[u]; i ^ -1; i = next[i])
	{
		v = to[i];
		if(!vis[v])
		{
			dfs(v);
			for(j = q; j >= 1; j--)
				for(k = 1; k <= j; k++)
					f[u][j] = max(f[u][j], f[u][j - k] + f[v][k - 1] + val[i]);
		}
	}
}

int main()
{
	int i, x, y, z;
	n = read();
	q = read();
	memset(head, -1, sizeof(head));
	for(i = 1; i < n; i++)
	{
		x = read();
		y = read();
		z = read();
		add(x, y, z);
		add(y, x, z);
	}
	dfs(1);
	printf("%d\n", f[1][q]);
	return 0;
}