UVA - 10034 Freckles

题意：最小生成树的模板题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
const int MAXN = 120;
const int INF = 0x3f3f3f3f;

double x[MAXN],y[MAXN],arc[MAXN][MAXN],low[MAXN];
int N;
int in[MAXN];

double dist(int i,int j){
    return (x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]);
}

double Prim_MST(){
    int p,i,j;
    double Min,cost=0.0;
    memset(in,0,sizeof(in));
    for (i = 1; i < N; i++)
        low[i] = arc[0][i];
    for (i = 1; i < N; i++){
        Min = INF;
        for (j = 1; j < N; j++)
            if (!in[j] && Min > low[j]){
                p = j;
                Min = low[j];
            }
        if (Min == INF)
            return -1;
        in[p] = 1;
        cost += sqrt(Min);
        for (j = 1; j < N; j++)
            if (!in[j] && low[j]>arc[p][j])
                low[j] = arc[p][j];
    }
    return cost;
}

int main(){
    int t;
    scanf("%d",&t);
    while (t--){
        scanf("%d",&N);
        for (int i = 0; i < N; i++)
            scanf("%lf%lf",&x[i],&y[i]);
        for (int i = 0; i < N; i++)
            for (int j = 0; j < i; j++)
                arc[i][j] = arc[j][i] = dist(i,j);
        printf("%.2lf\n",Prim_MST());
        if (t)
            printf("\n");
    }
    return 0;
}