hdu 4424 Conquer a New Region 并查集

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn=2e5+9;
int n;
int fa[maxn];
long long sum[maxn],son[maxn];
struct E
{
int from,to,w;
bool operator <(const E &xx) const
{
return w<xx.w;
}
}e[maxn];

int find(int x)
{
if(fa[x]!=x) fa[x]=find(fa[x]);
return fa[x];
}

void merge(int a,int b,int w)
{
int f1=find(a);
int f2=find(b);
long long mmax=max(sum[f1]+son[f2]*w,sum[f2]+son[f1]*w);
sum[f1]=mmax;
fa[f2]=f1;
son[f1]+=son[f2];
}

int main()
{
//    freopen("in.txt","r",stdin);
while(scanf("%d",&n)!=EOF)
{
for(int i=1;i<n;i++)
scanf("%d%d%d",&e[i].from,&e[i].to,&e[i].w);
sort(e+1,e+n);
for(int i=1;i<=n;i++) fa[i]=i,son[i]=1,sum[i]=0;

for(int i=n-1;i>=1;i--)
{
merge(e[i].from,e[i].to,e[i].w);
}
cout<<sum[find(1)]<<endl;
}
return 0;
}