hdu 4118 树形dp

思路：其实就是让每一条路有尽量多的人走。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<cstdio>
#include<vector>
#include<string>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define Maxn 100010
#define Maxm 100010
#define LL __int64
#define Abs(x) ((x)>0?(x):(-x))
#define lson(x) (x<<1)
#define rson(x) (x<<1|1)
#define inf 0x7fffffff
#define Mod 1000000007
using namespace std;
struct Edge{
    int u,v,next;
    LL val;
}edge[Maxm*2];
LL dp[Maxn],sum[Maxn],n;
int e,vi[Maxn],head[Maxn];
void init()
{
    memset(dp,0,sizeof(dp));
    memset(sum,0,sizeof(sum));
    memset(head,-1,sizeof(head));
    memset(vi,0,sizeof(vi));
    e=0;
}
void add(int u,int v,LL val)
{
    edge[e].u=u,edge[e].v=v,edge[e].val=val,edge[e].next=head[u],head[u]=e++;
    edge[e].u=v,edge[e].v=u,edge[e].val=val,edge[e].next=head[v],head[v]=e++;
}
void dfs(int u)
{
    int i,v;
    sum[u]=1;
    dp[u]=0;
    vi[u]=1;
    for(i=head[u];i!=-1;i=edge[i].next){
        v=edge[i].v;
        if(vi[v]) continue;
        dfs(v);
        LL num=min(sum[v],n-sum[v]);
        dp[u]+=dp[v]+num*edge[i].val*2;
        sum[u]+=sum[v];
    }
   // cout<<u<<" "<<dp[u]<<endl;
}
int main()
{
    int t,i,j,u,v,Case=0;
    LL val;
    scanf("%d",&t);
    while(t--){
        init();
        scanf("%I64d",&n);
        for(i=1;i<n;i++){
            scanf("%d%d%I64d",&u,&v,&val);
            add(u,v,val);
        }
        dfs(1);
        printf("Case #%d: %I64d
",++Case,dp[1]);
    }
    return 0;
}