HDU 4424 Conquer a New Region 并查集

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
template <class T>
inline bool rd(T &ret) {
	char c; int sgn;
	if (c = getchar(), c == EOF) return 0;
	while (c != '-' && (c<'0' || c>'9')) c = getchar();
	sgn = (c == '-') ? -1 : 1;
	ret = (c == '-') ? 0 : (c - '0');
	while (c = getchar(), c >= '0'&&c <= '9') ret = ret * 10 + (c - '0');
	ret *= sgn;
	return 1;
}
template <class T>
inline void pt(T x) {
	if (x <0) {
		putchar('-');
		x = -x;
	}
	if (x>9) pt(x / 10);
	putchar(x % 10 + '0');
}
using namespace std;
typedef long long ll;
const int N =  200100;
struct Edge{
    int u, v, d;
}edge
;
bool cmp(const Edge &x, const Edge&y){
    return x.d > y.d;
}
Edge add(int u, int v, int d){
    Edge E = {u, v, d};
    return E;
}
int n;
int fa
, num
;
ll sum
;
void init(){
    memset(sum, 0, sizeof sum);
    for(int i = 1; i <= n; i++)
        fa[i] = i, num[i] = 1;
}
int find(int x){return x==fa[x]?x:fa[x] = find(fa[x]);}
void Union(int x, int y, ll ans){
    num[x] += num[y];
    fa[y] = x;
    sum[x] += ans ;
}
ll work(){
    for(int i = 1; i < n; i++)
    {
        int fx = find(edge[i].u);
        int fy = find(edge[i].v);
        ll a = (ll)num[fy]*(ll)edge[i].d + sum[fx];
        ll b = (ll)num[fx]*(ll)edge[i].d + sum[fy];
        if(a>b)
            Union(fx, fy, a-sum[fx]);
        else
            Union(fy, fx, b-sum[fy]);
    }
    return sum[find(1)];
}
void input(){
    for(int i = 1, u, v, d; i < n; i++)
    {
        rd(u); rd(v); rd(d);
        edge[i] = add(u,v,d);
    }
    sort(edge+1, edge+n, cmp);
}
int main(){
    while (cin>>n){
        init();
        input();
        cout<<work()<<endl;
	}
	return 0;
}