HDU 1162 Eddy's picture(最小生成树)

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int maxn=100+10;
const int maxm=10000+10;

struct Edge
{
    int u,v;
    double dist;
    Edge(){}
    Edge(int u,int v,double dist):u(u),v(v),dist(dist){}
    bool operator<(const Edge &rhs)const
    {
        return dist<rhs.dist;
    }
};

struct Kruskal
{
    int n,m;
    Edge edges[maxm];
    int fa[maxn];
    int findset(int x){ return fa[x]==-1? x:fa[x]=findset(fa[x]); }

    void init(int n)
    {
        this->n=n;
        m=0;
        memset(fa,-1,sizeof(fa));
    }

    void AddEdge(int u,int v,double dist)
    {
        edges[m++]=Edge(u,v,dist);
    }

    double kruskal()
    {
        double sum=0;
        int cnt=0;
        sort(edges,edges+m);

        for(int i=0;i<m;i++)
        {
            int u=edges[i].u, v=edges[i].v;
            if(findset(u) != findset(v))
            {
                fa[findset(u)] = findset(v);
                sum +=edges[i].dist;
                if(++cnt>=n-1) return sum;
            }
        }
        return -1;
    }
}KK;

struct Point
{
    double x,y;
}p[maxn];
double get_dist(int i,int j)
{
    return sqrt((p[i].x-p[j].x)*(p[i].x-p[j].x)+(p[i].y-p[j].y)*(p[i].y-p[j].y));
}
int main()
{
    int n;
    while(scanf("%d",&n)==1)
    {
        KK.init(n);
        for(int i=0;i<n;i++)
            scanf("%lf%lf",&p[i].x,&p[i].y);
        for(int i=0;i<n;i++)
        for(int j=i+1;j<n;j++)
            KK.AddEdge(i,j,get_dist(i,j));
        printf("%.2lf\n",KK.kruskal());
    }
    return 0;
}