UVA 10034 Freckles

利用并查集求最短路，注意浮点数，再就是需要准备一下边集。

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#define MAXN 5000 + 100
#define MAXN1 100 + 10
int n, m, p1, p[MAXN1],r[MAXN],u[MAXN],v[MAXN];
double  w[MAXN], x[MAXN1], y[MAXN1];

int cmp(const void *_p, const void *_q)
{
    int *p = (int *)_p;
    int *q = (int *)_q;
    return w[*p] > w[*q] ? 1 : -1;
}

int find(int x) {return p[x] == x ? x : p[x] = find(p[x]);}

void kruskal()
{
    double ans = 0;
    for(int i = 0; i < m; i ++) p[i] = i;
    for(int i = 0; i < p1; i ++) r[i] = i;
    qsort(r, p1, sizeof(r[0]),cmp);
    for(int i = 0; i < p1; i ++)
    {
        int e = r[i]; int s = find(u[e]); int o = find(v[e]);
        if(s != o) { ans += w[e]; p[s] = o;}
    }
    printf("%.2lf\n",ans);
}

void solve()
{
     p1 = 0;
    for(int i = 0; i < m; i ++)
        for(int j = i + 1; j < m; j ++)
        {
            w[p1] = sqrt((x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]));
            u[p1] = i;
            v[p1] = j;
            p1 ++;
        }
    kruskal();
}

void init()
{
    while(~scanf("%d",&n))
        while(n --)
        {
            scanf("%d",&m);
            for(int i = 0; i < m; i ++)
                scanf("%lf%lf",&x[i],&y[i]);
            solve();
            if(n) puts("");
        }
}

int main()
{
    init();
    return  0;
}