hdu1875 畅通工程再续最小生成树

Posted 2022-11-23

题目链接：​​http://acm.hdu.edu.cn/showproblem.php?pid=1875​​​
题意：中文题
解析：建图后直接跑kruskal最小生成树，然后判断并查集后有是否有多个集合

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5+100;
struct node

    int u,v;
    double c;
    node() 
    node(int _u,int _v,double _c)
    
        u = _u;
        v = _v;
        c = _c;
    
    bool operator < (const node &b)const
    
        return c<b.c;
    
res[maxn];
struct point

    double x,y;
a[maxn];
double dis(point p1,point p2)

    return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));

int fa[maxn];
int getFa(int x)

    if(x==fa[x])
        return fa[x];
    return fa[x] = getFa(fa[x]);

int main(void)

    int t;
    scanf("%d",&t);
    while(t--)
    
        int n;
        scanf("%d",&n);
        for(int i=0;i<=n;i++)
            fa[i] = i;
        for(int i=1;i<=n;i++)
            scanf("%lf %lf",&a[i].x,&a[i].y);
        int cnt = 0;
        for(int i=1;i<=n;i++)
        
            for(int j=i+1;j<=n;j++)
            
                double d = dis(a[i],a[j]);
                if(d>=10 && d<=1000)
                    res[cnt++] = node(i,j,d*100.0);
            
        
        sort(res,res+cnt);
        double ans = 0;
        for(int i=0;i<cnt;i++)
        
            int t1 = getFa(res[i].u);
            int t2 = getFa(res[i].v);
            if(t1!=t2)
            
                ans += res[i].c;
                fa[t1] = t2;
            
        
        cnt = 0;
        for(int i=1;i<=n;i++)
        
            if(fa[i]==i)
                cnt++;
        
        if(cnt>1)
            puts("oh!");
        else
            printf("%.1f\\n",ans);
    
    return 0;