poj3625 Building Roads(最小生成树)

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
#define inf 0x3f3f3f3f
struct node
{
int x,y;
}edge[1500];
int n,m;
double map[1500][1500];
double fun(int x1,int x2,int y1,int y2)
{
return sqrt((double)(x1-x2)*(x1-x2)+(double)(y1-y2)*(y1-y2));//注意转换成double
}
double d[1500];
int vis[1500];
void prim()
{
for(int i=1;i<=n;i++)
{
d[i]=map[1][i];
}
memset(vis,0,sizeof(vis));
d[1]=(double)0;
vis[1]=1;
double tmp;
int v;
for(int i=1;i<=n;i++)
{
tmp=(double)inf;
for(int j=1;j<=n;j++)
{
if(!vis[j]&&d[j]<tmp)
{
tmp=d[j];
v=j;
}
}
vis[v]=1;
for(int j=1;j<=n;j++)
{
if(!vis[j]&&d[j]>map[v][j])
{
d[j]=map[v][j];
}
}
}
double ans=(double)0;
for(int i=1;i<=n;i++)
{
if(d[i]==(double)-1)continue;
ans+=d[i];
}
printf("%.2f\n",ans);
}
int main()
{
scanf("%d %d",&n,&m);
for(int i=1;i<=n;i++)
{
scanf("%d %d",&edge[i].x,&edge[i].y);
}
for(int i=1;i<=n;i++)
{
for(int j=i+1;j<=n;j++)
{
map[j][i]=map[i][j]=fun(edge[i].x,edge[j].x,edge[i].y,edge[j].y);
}
}
for(int i=1;i<=m;i++)
{
int a,b;
scanf("%d %d",&a,&b);
map[a][b]=map[b][a]=(double)-1;
}
prim();
}