poj 2560（prime）

一：
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
using namespace std;
#define MAXN 150
#define inf 99999999
double map[MAXN][MAXN],x[MAXN],y[MAXN],dis[MAXN];
int mark[MAXN];
double prime (int n)
{
    int i,j,min,now=0;
    double ans=0;

    memset(mark,0,sizeof(mark));
    for(i=0;i<n;i++)
        dis[i]=inf;
    for(i=0;i<n;i++)
    {
        double mie=inf;
        for(j=0;j<n;j++)
        {
            if(!mark[j])
            {
                if(dis[j]>map[now][j])
                    dis[j]=map[now][j];        
                if(dis[j]<mie)
                {
                    mie=dis[j];
                    min=j;
                }
            }
        }
        now=min;
        mark[now]=1;
    }
    for(i=0;i<n;i++)
        ans+=dis[i];
    return ans;
}
double mydis(int i,int j)
{
    double a=x[i]-x[j];
    double b=y[i]-y[j];
    return sqrt(a*a+b*b);
}
int main()
{
    int n,i,j;
    while(scanf("%d",&n)!=EOF)
    {
        for(i=0;i<n;i++)
            scanf("%lf%lf",&x[i],&y[i]);

        memset(map,0,sizeof(map));
        for(i=0;i<n;i++)
            for(j=0;j<n;j++)
                map[i][j]=map[j][i]=mydis(i,j);
    printf("%.2f\n",prime(n));
    }
    return 0;
}

二：
#include<iostream>
#include<cmath>
#define min(a,b) ((a)<(b)?(a):(b))
using namespace std;
const int Max = 105;
const double inf = 99999999;
 
struct Point{
    double x, y;
}p[Max];
double map[Max][Max], dis[Max];
 
double prim(int n){
    int i, j, mi_n, now = 0;
    double mi_e, ans = 0;
    for(i = 0; i < n; i ++)
        dis[i] = inf;
    for(i = 1; i < n; i ++){
        dis[now] = -1;
        mi_e = inf;
        for(j = 0; j < n; j ++)
            if(now != j && dis[j] >= 0){
                dis[j] = min(dis[j], map[now][j]);
                if(dis[j] < mi_e){
                    mi_e = dis[j];
                    mi_n = j;
                }
            }
        now = mi_n;
        ans += mi_e;
    }
    return ans;
}
 
double mydis(int i, int j){
    double a = p[i].x - p[j].x;
    double b = p[i].y - p[j].y;
    return sqrt(a*a + b*b);
}
 
int main(){
    int n, i, j;
    while(scanf("%d", &n) != EOF){
        for(i = 0; i < n; i ++){
            scanf("%lf%lf", &p[i].x, &p[i].y);
            for(j = 0; j < i; j ++)
                map[i][j] = map[j][i] = mydis(i, j);
        }
        printf("%.2lf\n", prim(n));
    }
    return 0;
}