题解：

类似最小生成树，先做最小生成树然后枚举顶点，删边和加边。

[cpp]?
#include?
#include?
#include?
#include?
#include?
using namespace std;?
const int maxn=1010*1010;?
struct NODE{?
??? int u,v;?
??? double w;?
??? bool operator < (const NODE &a) const?
??? {?
??????? return a.w>w;?
??? }?
}node[maxn*2],in[1005];?
?
struct TREE?
{?
??? int u,next;?
??? double w;?
}tree[maxn*5];?
int head[1010];?
bool vis[1010];?
int f[1005];?
double g[1010][1010];?
int find(int x)?
{?
??? return f[x]==x? x:f[x]=find(f[x]);?
}?
int val[1005];?
void dfs(int root,int x)?
{?
??? vis[x]=true;?
??? for(int i=head[x];i!=-1;i=tree[i].next)?
??? if(!vis[tree[i].u])?
??? {?
??????? g[root][tree[i].u]=max(tree[i].w,g[root][x]);?
??????? dfs(root,tree[i].u);?
??? }?
}?
void kruskal(int n,int e)?
{?
??? memset(head,-1,sizeof(head));?
??? double sum=0,ans=0;?
??? int p=0;?
??? for(int i=0;i<=n;i++)??? f[i]=i;?
??? sort(node,node+e);?
?
??? for(int i=0;i ??? {?
??????? int x=find(node[i].u);?
??????? int y=find(node[i].v);?
??????? if(x!=y)?
??????? {?
??????????? sum+=node[i].w;?
??????????? f[y]=x;?
?
??????????? //tree?
??????????? tree[p].u=node[i].u;tree[p].w=node[i].w;?
??????????? tree[p].next=head[node[i].v];head[node[i].v]=p++;?
??????????? tree[p].u=node[i].v;tree[p].w=node[i].w;?
??????????? tree[p].next=head[node[i].u];head[node[i].u]=p++;?
??????? }?
??? }?
?
??? for(int i=0;i<=n;i++)?
???? for(int j=0;j<=n;j++)?
????? g[i][j]=0;?
?
??? for(int i=1;i<=n;i++)?
??? {?
??????? for(int j=0;j<=n;j++)?
??????? vis[j]=false;?
??????? dfs(i,i);?
??? }?
?
??? //g[i][j]?
?
??? for(int i=1;i<=n;i++)?
???? for(int j=i+1;j<=n;j++)?
??????? ans=max(ans,(val[i]+val[j])/(sum-g[i][j]));?
?
??? printf("%.2f\n",ans);?
}?
int main()?
{?
??? int ca,n,num;?
??? int x[1005],y[1005];?
??? scanf("%d",&ca);?
??? while(ca--)?
??? {?
??????? scanf("%d",&n);?
??????? num=0;?
??????? for(int i=1;i<=n;i++)?
??????? {?
??????????? scanf("%d%d%d",&x[i],&y[i],&val[i]);?
??????? }?
??????? for(int i=1;i<=n;i++)?
??????? {?
??????????? for(int j=i+1;j<=n;j++)?
??????????? {?
??????????????? node[num].u=i;?
??????????????? node[num].v=j;?
??????????????? node[num].w=sqrt(((x[i]-x[j])*(x[i]-x[j]))+((y[i]-y[j])*(y[i]-y[j])));?
??????????????? num++;?
??????????? }?
??????? }?
??????? kruskal(n,num);?
??? }?
??? return 0;?
}?