hdu 3938 并查集

思路：这题的出题人是不是语文不行啊，题目意思说不清楚。

知道是求存在路径的点对数后，用并查集每次记录集合中点的数目，很容易就解决了。

#include<set>
#include<cmath>
#include<queue>
#include<cstdio>
#include<vector>
#include<string>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pb push_back
#define mp make_pair
#define Maxn 200100
#define Maxm 800002
#define LL __int64
#define Abs(x) ((x)>0?(x):(-x))
#define lson(x) (x<<1)
#define rson(x) (x<<1|1)
#define inf 1000000000
#define lowbit(x) (x&(-x))
#define Mod 1000000007
using namespace std;
int fa[Maxn],cnt;
LL num[Maxn],ans[Maxn];
struct Edge{
    int u,v,val;
    int operator< (const Edge &temp) const
    {
        return val<temp.val;
    }
}p[Maxm];
struct Query{
    int val,id;
    int operator< (const Query &temp) const{
        return val<temp.val;
    }
}q[Maxn];
void init()
{
    for(int i=0;i<Maxn;i++){
        fa[i]=i;
        ans[i]=0;
        num[i]=1;
    }
}
int find(int x)
{
    if(x!=fa[x])
        fa[x]=find(fa[x]);
    return fa[x];
}
LL merg(int a,int b)
{
    int x=find(a);
    int y=find(b);
    if(x==y) return 0;
    LL ans=num[x]*num[y];
    num[x]+=num[y];
    fa[y]=x;
    ++cnt;
    return ans;
}
int main()
{
    int n,m,t,i,j,u,v;
    while(scanf("%d%d%d",&n,&m,&t)!=EOF){
        init();
        for(i=1;i<=m;i++){
            scanf("%d%d%d",&p[i].u,&p[i].v,&p[i].val);
        }
        for(i=1;i<=t;i++)
            scanf("%d",&q[i].val),q[i].id=i;
        sort(p+1,p+1+m);
        sort(q+1,q+1+t);
        p[m+1].val=inf;
        p[m+1].u=1,p[m+1].v=1;
        j=1;
        LL sum=0;
        cnt=0;
        int pos=1;
        for(i=1;i<=m+1;i++){
            while(j<=t&&q[j].val<p[i].val){
                ans[q[j].id]=sum;
                j++;
            }
            sum+=merg(p[i].u,p[i].v);
        }
        while(j<=t&&q[j].val<p[i].val)
        {
            ans[q[j].id]=sum;
                j++;
        }
        for(i=1;i<=t;i++){
            printf("%I64d\n",ans[i]);
        }
    }
    return 0;
}