hdu1162最小生成树

/*    Made by Karen    16:40p.m. at Mar.4,2012    prim算法求最小生成树    同hdu1875 而且在main函数里面的处理更简单*/#include <iostream>#include <cstdio>#include <math.h>using namespace std;#define MAX_Point   110#define MAX_Edge    12100#define INF 99999999double arr_list[110][110];struct point{    double x;    double y;}point[MAX_Point];struct Edge{    int pointer;    double lowcost;    int flag;}edge[MAX_Edge];double prim(int n){    int i,j,k=1,flag;    double min,sum2=0;    j=1;    for(i=1;i<=n;i++)    {        edge[i].pointer=i;        edge[i].lowcost=arr_list[j][i];        edge[i].flag=0;    }    edge[j].flag=1;    edge[j].lowcost=0;    for(i=2;i<=n;i++)    {        k=1;        min=INF;        flag=0;        for(j=2;j<=n;j++)        {            if(edge[j].flag==0&&edge[j].lowcost<min)            {                k=j;                min=edge[j].lowcost;                flag=1;            }        }        if(!flag)   return -1;        edge[k].flag=1;        sum2+=min;        for(j=2;j<=n;j++)        {            if(edge[j].flag==0&&arr_list[k][j]<edge[j].lowcost)            {                edge[j].pointer=k;                edge[j].lowcost=arr_list[k][j];            }        }    }    return sum2;}int main(){    int n,i,j;    double tmp,ans;    while(scanf("%d",&n)!=EOF)    {        for(i=0;i<=100;i++)            for(j=0;j<=100;j++)                arr_list[i][j]=INF;        for(i=1;i<=n;i++)            scanf("%lf%lf",&point[i].x,&point[i].y);        for(i=1;i<=n;i++)            for(j=1;j<=n;j++)            {                tmp=sqrt((point[i].x-point[j].x)*(point[i].x-point[j].x)+(point[i].y-point[j].y)*(point[i].y-point[j].y));                arr_list[i][j]=tmp;            }        ans=prim(n);        printf("%.2lf\n",ans);    }    return 0;}