HDU 1875 畅通工程再续

题目链接：https://vjudge.net/problem/HDU-1875

思路：

最小生成树板子，建图的时候把小于10或者大于1000的边给删了。

#include <stdio.h>
#include <iostream>
#include <queue>
#include <math.h>
using namespace std;

const int N = 110;
const double inf = 1e9;
double g[N][N];

struct City{
    double dis;
    bool vis;
}city[N];
struct Place{
    double x;
    double y;
}p[N];
struct node{
    int loc;
    double w;

    bool friend operator<(const node& a,const node& b){
        return a.w > b.w;
    }
};
priority_queue<node > que;

void init(int& n){

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

        city[i].dis = inf;
        city[i].vis = 0;
        for(int j = 1; j <= n; j++)
            if(i == j) g[i][j] = 0;
            else g[i][j] = inf;
    }
}

double inline dist(int a,int b){
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)+(p[a].y-p[b].y)*(p[a].y-p[b].y));
}

void get_map(int& n){

    double tmp_d;
    for(int i = 1; i <= n; i++)
        for(int j = i+1; j <= n; j++){
            tmp_d = dist(i,j);
            if(tmp_d >= 10 && tmp_d <= 1000)
                g[i][j] = g[j][i] = tmp_d;
        }
}

void prime(double& ans,int& n){

    while(!que.empty()) que.pop();
    que.push(node{1,0});
    city[1].dis = 0;

    int u;
    while(!que.empty()){
        u = que.top().loc;
        que.pop();
        city[u].vis = 1;

        for(int v = 1; v <= n; v++){
            if(!city[v].vis && city[v].dis > g[u][v]){
                city[v].dis = g[u][v];
                que.push(node{v,city[v].dis});
            }
        }
    }

    for(int i = 1; i <= n; i++){
        if(city[i].dis == inf){
            ans = 0;
            return;
        }
        ans += city[i].dis;
    }

}

int main(){

    int T;
    while(~scanf("%d",&T)){

        while(T--){
            int n;
            scanf("%d",&n);

            init(n);

            for(int i = 1; i <= n; i++)
                scanf("%lf%lf",&p[i].x,&p[i].y);

            get_map(n);

            double ans = 0;
            prime(ans,n);
            if(!ans) printf("oh!
");
            else printf("%.1f
",ans*100);
        }
    }

    return 0;
}