//dp[u][k1]=min(dp[u][k1-k2]+dp[v][k2]+edge*k2*(k-k2))
//dp[u][k]表示以u节点为根节点的子树中选k个节点所得的最优解
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
const int maxn=2010;
const __int64 inf=1e18;
int nedge;
struct node
{
int u,v,w,next;
}edge[2*maxn];
int head[maxn];
__int64 dp[maxn][maxn];
int n,k;
void addedge(int u,int v,int w)
{
edge[nedge].u=u;
edge[nedge].v=v;
edge[nedge].w=w;
edge[nedge].next=head[u];
head[u]=nedge++;
}
void dfs(int u,int pre)
{
int i;
dp[u][1]=0;
for(i=head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].v;
int w=edge[i].w;
if(v==pre)continue;
dfs(v,u);
int k1,k2;
for(k1=k;k1>=0;k1--)
{
for(k2=1;k2<=k1;k2++)
{
dp[u][k1]=min(dp[u][k1],dp[u][k1-k2]+dp[v][k2]+w*k2*(k-k2)*2);
}
}
}
}
void init()
{
int i,j;
memset(head,-1,sizeof(head));
memset(edge,0,sizeof(edge));
for(i=1;i<=n;i++)
for(j=1;j<=n;j++)
dp[i][j]=inf;
nedge=0;
}
int main()
{
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
int T;
scanf("%d",&T);
while(T--)
{
scanf("%d%d",&n,&k);
init();
int a,b,c;
n--;
while(n--)
{
scanf("%d%d%d",&a,&b,&c);
addedge(a,b,c);
addedge(b,a,c);
}
dfs(1,0);
printf("%I64d\n",dp[1][k]);
}
return 0;
}
hdu 5148Cities 树形dp
原文：http://blog.csdn.net/cq_pf/article/details/44099257
