zoj 3659 Conquer a New Region(并查集)

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;

const int maxn = 200005;

struct Edge
{
int u,v,w;
Edge(int u=0,int v=0,int w=0): u(u), v(v), w(w) {}
bool operator < (const Edge& rhs) const
{
return w > rhs.w;
}
}edges[maxn];

int counts[maxn];
int pa[maxn];
long long cap[maxn];

int find(int x)
{
return x == pa[x] ? x : pa[x] = find(pa[x]);
}

int main()
{
//freopen("E:\\acm\\input.txt","r",stdin);
int N;
while(cin>>N)
{
for(int i=1; i<=N; i++)
{
counts[i] = 1;
pa[i] = i;
cap[i] = 0;
}

for(int i=1; i<N; i++)
{
int a,b,c;
scanf("%d %d %d",&a,&b,&c);
edges[i] = Edge(a,b,c);
}
sort(edges+1,edges+N);

long long ans = 0;
for(int i=1; i<N; i++)
{
long long w = edges[i].w;
int u_fa = find(edges[i].u);
int v_fa = find(edges[i].v);

//下面目的是维护根到集合中所有的点cap值最大
long long Lu = cap[u_fa] + w*counts[v_fa];
long long Rv = cap[v_fa] + w*counts[u_fa];
if(Lu > Rv)
{
pa[v_fa] = u_fa;
cap[u_fa] = Lu;
counts[u_fa] += counts[v_fa];
}
else
{
pa[u_fa] = v_fa;
cap[v_fa] = Rv;
counts[v_fa] += counts[u_fa];
}
}
for(int i=1; i<=N; i++)
ans = max(ans,cap[i]);
cout<<ans<<"\n";
}
}