Prim 模板 POJ 3625

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
const int maxn=1000+5;
int n,m,vis[maxn];
double mp[maxn][maxn],low[maxn];
struct node{
    int x,y;
}s[maxn];
inline double calc(int x,int y){
    return sqrt((double)(s[x].x-s[y].x)*(double)(s[x].x-s[y].x)+(double)(s[x].y-s[y].y)*(double)(s[x].y-s[y].y));
}
inline double prim(void){
    double ans=0;
    int pos;
    memset(vis,0,sizeof(vis));//²»ÔÚV¼¯ºÏÖÐ
    vis[1]=1,pos=1;
    for(int i=2;i<=n;i++)
        low[i]=mp[1][i];
    for(int i=1;i<n;i++){
        double MIN=0x3f3f3f3f;
        for(int j=1;j<=n;j++)
            if(!vis[j]&&low[j]<MIN)
                MIN=low[j],pos=j;
        ans+=MIN,vis[pos]=1;
        for(int j=1;j<=n;j++)
            if(low[j]>mp[pos][j]&&!vis[j])
                low[j]=mp[pos][j];
    }
    return ans;
}
signed main(void){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
        scanf("%d%d",&s[i].x,&s[i].y);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            if(i!=j)
                mp[i][j]=mp[j][i]=calc(i,j);
    for(int i=1,x,y;i<=m;i++)
        scanf("%d%d",&x,&y),mp[x][y]=mp[y][x]=0;
    printf("%.2f",prim());
    return 0;
}

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by >_< neighthorn