Building a Space Station POJ

题目链接：https://vjudge.net/problem/POJ-2031

思路：最小生成树板子题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <stack>
#include <string>
#include <map>
#include <cmath>
using namespace std;
 
typedef long long LL;
#define inf 1e11
#define rep(i,j,k) for(int i = (j); i <= (k); i++)
#define rep__(i,j,k) for(int i = (j); i < (k); i++)
#define per(i,j,k) for(int i = (j); i >= (k); i--)
#define per__(i,j,k) for(int i = (j); i > (k); i--)

const int N = 110;
int head[N];
int cnt;
double dis[N];
bool vis[N];
int n;

struct Point{
    double x,y,z,r;
}p[N];

struct Edge{
    int to;
    double w;
    int nxt;
}e[N*N];

struct node{
    int u;
    double w;
    friend bool operator<(const node& a,const node& b){
        return a.w > b.w;
    }
};

priority_queue<node > que;

void add(int u,int v,double w){
    e[cnt].to = v;
    e[cnt].w = w;
    e[cnt].nxt = head[u];
    head[u] = cnt++;
}

inline double get_dis(Point& a,Point& b){
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z))-a.r-b.r;
}

double prime(){
    while(!que.empty()) que.pop();

    rep(i,1,n){
        vis[i] = false;
        dis[i] = inf;
    }
    dis[1] = 0;
    que.push(node{1,dis[1]});
   
    int u,v;
    double w;
    while(!que.empty()){
        u = que.top().u;
        que.pop();
        if(vis[u]) continue;
        vis[u] = true;

        for(int o = head[u]; ~o; o = e[o].nxt){
            v = e[o].to;
            w = e[o].w;

            if(!vis[v] && dis[v] > w){
                dis[v] = w;
                que.push(node{v,dis[v]});
            }
        }
    }

    double ans = 0;
    rep(i,1,n) ans += dis[i];
    return ans;
}

int main(){

    double tmp;
    while(~scanf("%d",&n)){
        if(n == 0) break;
        rep(i,1,n) head[i] = -1;
        cnt = 0;

        rep(i,1,n) scanf("%lf%lf%lf%lf",&p[i].x,&p[i].y,&p[i].z,&p[i].r);
//        rep(i,1,n) printf("%.3f %.3f %.3f %.3f
",p[i].x,p[i].y,p[i].z,p[i].r);

        rep(i,1,n) rep(j,i+1,n){
            tmp = get_dis(p[i],p[j]);
            add(i,j,tmp > 0 ? tmp : 0);
            add(j,i,tmp > 0 ? tmp : 0);
        }

        printf("%.3f
",prime());
    }

    getchar(); getchar();
    return 0;
}