UVA 10397 - Connect the Campus

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#define MAXN 800
#define MAXN1 300000

double x[MAXN], y[MAXN], w[MAXN1];
int n, p1, m, p[MAXN], u[MAXN1], v[MAXN1], r[MAXN1], vis[1010][1010];

int cmp(const void *_i, const void *_j)
{
int *i = (int *)_i;
int *j = (int *)_j;
return w[*i] > w[*j] ? 1 : -1;
}
int find(int x) {return p[x] == x ? x : p[x] = find(p[x]);}
double kruskal()
{
double ans = 0;
for(int i = 0; i <= n; 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 x1 = find(u[e]); int y1 = find(v[e]);
if(x1 != y1){ans += w[e]; p[x1] = y1;}
}
return ans;
}

void init()
{
while(~scanf("%d",&n))
{
memset(vis,0,sizeof(vis));
for(int i = 1; i <= n; i ++)
scanf("%lf%lf",&x[i], &y[i]);
scanf("%d",&m);
for(int i = 0; i < m; i ++)
{
int z, c;
scanf("%d%d",&z, &c);
if(z > c) vis[c][z] = 1;
else vis[z][c] = 1;
}
p1 = 0;
for(int i = 1; i <= n; i ++)
{
for(int j = i+1; j <= n; j ++)
{
if(vis[i][j]) w[p1] = 0;
else
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 ++;
}
}
printf("%.2f\n",kruskal());
}
}
int main()
{
init();
return 0;
}