Los P1265 Valley highway construction minimum spanning tree

Los P1265 Valley highway construction minimum spanning tree

answer:

We need to build a complete graph , the number of edges may be large , so the use of prim algorithm is better.

code show as below:

#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<cmath>
#include<queue>
#include<cstring>
#include<vector>
#include<map>
#define MAX 5005
#define INF 0x3f3f3f3f
typedef long long ll;
using namespace std;

int n;//n个结点
int visit[MAX];
double dis[MAX];

struct node{
    ll x,y;
};

vector<node> vec;

void prim(){//prim算法
    for(int i=0;i<MAX;i++){
        visit[i]=0;
        dis[i]=INF;
    }
    dis[1]=0;
    for(int i=0;i<=n;i++){
        int minl=INF,u=-1;
        for(int j=1;j<=n;j++){
            if(visit[j]==0&&dis[j]<minl){
                minl=dis[j];
                u=j;
            }
        }
        if(u==-1) break;
        visit[u]=1;
        node t1=vec[u];
        for(int v=1;v<=n;v++){
            node t2=vec[v];
            double tmp=sqrt((t1.x-t2.x)*(t1.x-t2.x)+(t1.y-t2.y)*(t1.y-t2.y));
            if(visit[v]==0&&tmp<dis[v]){
                dis[v]=tmp;
            }
        }
    }
}

int main(){
    scanf("%d",&n);
    vec.resize(n+1);
    for(int i=1;i<=n;i++){
        scanf("%lld%lld",&vec[i].x,&vec[i].y);
    }
    prim();
    double ans=0.0;
    for(int i=1;i<=n;i++){
        ans+=dis[i];
    }
    printf("%.2f",ans);
    return 0;
}