OJ-Problems-Source/HDOJ/2376_autoAC.cpp
2016-08-22 00:13:12 +08:00

60 lines
1.2 KiB
C++

#include <iostream>
#include <string.h>
#include <stdio.h>
using namespace std;
#define N 10010
struct note
{
int v,next,value;
}edge[N*2+10];
int head[N];
double dp[N];
int sum[N];
int n;
int kk;
int ss;
void add(int fa,int son,int value)
{
edge[kk].v = son;
edge[kk].value = value;
edge[kk].next = head[fa];
head[fa] = kk++;
}
void dfs(int root,int fa)
{
sum[root] = 1;
for(int i = head[root];i != -1;i = edge[i].next)
{
int son = edge[i].v;
if(son == fa) continue;
dfs(son,root);
sum[root] += sum[son];
ss += sum[son]*(n-sum[son]);
dp[root] += dp[son] + (double)sum[son]*(n-sum[son])*edge[i].value;
}
}
int main()
{
int cas;
scanf("%d",&cas);
while(cas--)
{
ss = 0;
memset(head,-1,sizeof(head));
memset(dp,0,sizeof(dp));
kk = 1;
scanf("%d",&n);
int a,b,v;
for(int i = 1;i < n;i++)
{
scanf("%d%d%d",&a,&b,&v);
add(a,b,v);
add(b,a,v);
}
dfs(0,-1);
ss = n*(n-1) / 2;
printf("%llf\n",(double)dp[0] / ss);
}
return 0;
}