poj3625

在已有的边上做Prim

#include<iostream>

#include<cmath>

#include<iomanip>

using namespace std;

#define infinity 1000000

 

class Point2D

{

public:

double x,y;

};

 

Point2D point[1001];

double map[1001][1001];

double dis[1001];

bool flag[1001];

int n,m;

 

int main()

{

memset(flag,false,sizeof(flag));

int c,i,j,k;

double len;

double minone;

scanf("%d%d",&n,&m);

for(i=1;i<=n;i++)

cin>>point[i].x>>point[i].y;

//初始化map

for(i=1;i<=n;i++)

map[i][i]=0;

 

for(i=1;i<=n;i++)

for(j=i+1;j<=n;j++)

{

map[i][j]=sqrt( pow(point[i].x-point[j].x,2)+pow(point[i].y-point[j].y,2) );

map[j][i]=map[i][j];

}

 

for(k=0;k<m;k++)

{

cin>>i>>j;

// len+=map[i][j];

map[j][i]=map[i][j]=0.0;

}

//下面用prim求最小生成树

for(k=1;k<=n;k++)

dis[k]=map[1][k];

flag[1]=true;

 

len=0.0;

for(c=1;c<n;c++)

{

minone=10000000.0;

for(i=1;i<=n;i++)

if(flag[i]==false && dis[i]<minone)

{

k=i;

minone=dis[i];

}

flag[k]=true;

len+=minone;

 

for(i=1;i<=n;i++)

if(flag[i]==false && map[k][i]<dis[i])

dis[i]=map[k][i];

}

 

cout<<setiosflags(ios::fixed)<<setprecision(2)<<len<<endl;

return 0;

}