uva 10034【Freckles】

Krustral是也。。。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>

struct segment 
{
    int u,v;
    double w;
}s[10000];

struct point
{
    double x,y;
}p[110];

int f[105];
int n;
int sum;
double len;

bool cmp(const segment &a,const segment &b)
{
    if(a.w == b.w)
        return a.u < b.u;
    return a.w < b.w;
}

double dis(point a,point b)
{
    return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y)*(a.y - b.y));
}

int find(int x)
{
    if(x == f[x])
        return x;
    f[x] = find(f[x]);

    return f[x];
}

void krustral()
{
    len = 0;
    for(int i = 0;i < sum;i ++)
    {
        int fa = find(s[i].u);
        int fb = find(s[i].v);
        if(fa != fb)
        {
            f[fa] = fb;
            len += s[i].w;
        }
    }
    printf("%.2lf\n",len);
}
int main()
{
    int cas;
    scanf("%d",&cas);
    while(cas --)
    {
        scanf("%d",&n);
        sum = 0;
        for(int i = 0;i < n;i ++)
        {
            scanf("%lf%lf",&p[i].x,&p[i].y);
            for(int j = 0;j < i;j ++)
            {
                s[sum].u = i;
                s[sum].v = j;
                s[sum ++].w = dis(p[i],p[j]);
            }
        }
        std::sort(s,s + sum,cmp);

        for(int i = 0;i <= n;i ++)
        {
            f[i] = i;
        }

        krustral();
        if(cas)
            printf("\n");
    }

    return 0;
}