UVALive - 4872 最小生成树

#include <iostream>
#include <cmath>
using namespace std;
long long INF = 1000000;
double cost[1005][1005];
double mincost[1005];
bool used[1005];
int vv;

double prim(){
for(int i = 0; i< vv; ++i){
mincost[i] = INF;
used[i] = false;
}
mincost[0] = 0;
double res = 0;

while(true){
int v = -1;
for(int u = 0; u < vv; u++){
if(!used[u] && (v== -1 || mincost[u] < mincost[v])) v = u;
}

if(v == -1) break;
used[v] = true;
res += mincost[v];
for(int u = 0; u < vv; u++){
mincost[u] = min(mincost[u], cost[v][u]);
}
}
return res;
}

int main(){
int n;
while(scanf("%d",&n)&&n){
int x[n+1], y[n+1];
vv=0;
for(int i = 0; i < n; i++){
scanf("%d%d", &x[vv], &y[vv]);
for(int j = 0; j < vv; j++){
cost[j][vv] =  sqrt((double)((x[vv]-x[j])*(x[vv]-x[j])+(y[vv]-y[j])*(y[vv]-y[j])));
cost[vv][j] = cost[j][vv];
}
vv++;
}
double d = prim();
printf("%.2lf\n",d);
}
}