【并查集】 HDU 4424 Conquer a New Region 贪心

题意：给出一棵树，树的边上都有边权值，求从一点出发的权值和最大，权值为从一点出去路径上边权的最小值  

边权从大到小排序后  每次合并

取总权值最大的为父亲节点

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <string>
#include <iostream>
#include <algorithm>
#include <sstream>
#include <cmath>
using namespace std;
#include <queue>
#include <stack>
#include <vector>
#include <deque>
#include <map>
#define cler(arr, val) memset(arr, val, sizeof(arr))
typedef long long LL;
const int MAXN = 555;
const int MAXM = 260110;
const int INF = 0x3f3f3f3f;
const int mod = 1000000007;
struct node
{
LL a1,b1;
LL v;
};
struct node a[200010];
LL father[200010],rank[200010];
LL dis[200010];///边权和
LL n;
bool cmp(node c1,node c2)
{
return c1.v>c2.v;
}
void init()
{
for(LL i=1; i<=n; i++)
{
father[i]=i;
dis[i]=0;
rank[i]=1;///以i为根的节点数
}
}
LL find(LL x)
{
if(x==father[x])
return x;
return father[x]=find(father[x]);
}
void Union(LL x,LL y,LL w)
{
father[x]=y;
rank[y]+=rank[x];
dis[y]=w;
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#endif
LL x1,x2;
while(~scanf("%lld",&n))
{
for(int i=1; i<n; i++)
scanf("%lld%lld%lld",&a[i].a1,&a[i].b1,&a[i].v);
init();
sort(a+1,a+n,cmp);
for(int i=1; i<n; i++)
{
LL fa=find(a[i].a1);
LL fb=find(a[i].b1);
x1=dis[fa]+a[i].v*rank[fb];
x2=dis[fb]+a[i].v*rank[fa];
if(x1>x2)
Union(fb,fa,x1);
else
Union(fa,fb,x2);
}
printf("%lld\n",dis[find(1)]);
}
return 0;
}