hdu 5148 cities 树形DP

#include <iostream>
#include <cstdio>
using namespace std;
typedef long long LL;
const double EPS = 1e-6;
const int INF = 0x3fffffff;
const LL LINF = INF * 1ll * INF;

using namespace std;

#define MAXN 5005

int head[MAXN],nxt[MAXN],e[MAXN],w[MAXN];
int cnt;
LL dp[MAXN][55];

//适用于正负整数
template <class T>
inline bool scan_d(T &ret) {
   char c; int sgn;
   if(c=getchar(),c==EOF) return 0; //EOF
   while(c!=‘-‘&&(c<‘0‘||c>‘9‘)) c=getchar();
   sgn=(c==‘-‘)?-1:1;
   ret=(c==‘-‘)?0:(c-‘0‘);
   while(c=getchar(),c>=‘0‘&&c<=‘9‘) ret=ret*10+(c-‘0‘);
   ret*=sgn;
   return 1;
}


void addEdge(int u,int v,int w){
    e[cnt] = v;
    ::w[cnt] = w;
    int tmp = head[u];
    head[u] = cnt;
    nxt[cnt++] = tmp;
}

int n,k;

void update(LL &ans,LL v){
    if(ans>v) ans = v;
}

void dfs(int u,int fa){
    for(int i = head[u];~i;i = nxt[i]){
        if(e[i]==fa) continue;
        dfs(e[i],u);
    }
    for(int i = 0;i<=k;i++) dp[u][i] = LINF;
    dp[u][1] = 0;
    for(int i = head[u];~i;i = nxt[i]){
        if(e[i]==fa) continue;
        int v = e[i];
        for(int a = k;a>=0;a--){
            for(int b = 1;a+b<=k;b++){
                if(dp[v][b]==LINF) break;
                update(dp[u][a+b],dp[u][a]+dp[v][b]+2ll*b*(k-b)*w[i]);
            }
        }
    }
}

int main(void){
#ifndef ONLINE_JUDGE
//    freopen("/Users/mac/Desktop/data.in","r",stdin);
#endif
    int t;
    scanf("%d",&t);
    while(t--){
        //scanf("%d %d",&n,&k);
        scan_d(n);
        scan_d(k);
        for(int i = 1;i<=n;i++) head[i] = -1;
        cnt = 0;
        for(int i = 0;i<n-1;i++){
            int u,v,w;
            scan_d(u);
            scan_d(v);
            scan_d(w);
            addEdge(u,v,w);
            addEdge(v,u,w);
        }
        LL ans = LINF;
        dfs(1,-1);
        for(int i = 1;i<=n;i++){
            update(ans,dp[i][k]);
        }
        printf("%I64d\n",ans);
    }
    return 0;
}