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;

}