HDU-1875(通畅工程再续) Kruskal

HDU-1875

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;

const int MAXN = 105;
const int MAXM = 105 * 104;

struct _Edge{
    int from, to;
    double dist;
    _Edge(){};
    _Edge(int _from, int _to, double _dist): from(_from), to(_to), dist(_dist){};
};
struct _Node{
    double x, y;
    _Node(){};
    _Node(double _x, double _y): x(_x), y(_y){};
};

_Node node[MAXN];
_Edge edge[MAXM];
int f[MAXN];

bool cmp(_Edge e1, _Edge e2){
    return e1.dist < e2.dist;
}
int find(int x){
    return f[x] == -1 ? x : f[x] = find(f[x]);
}
double Kruskal(int cnt, int n){
    memset(f, -1, sizeof(f));
    sort(edge, edge + cnt, cmp);
    double res = 0;
    int t = 0;
    for(int i = 0; i < cnt; ++i){
        int a = find(edge[i].from);
        int b = find(edge[i].to);
        if(a != b){ 
            f[a] = b;
            res += edge[i].dist;
            t++;
        }
        if(t == n - 1) break;
    }
    if(t < n - 1) return -1;
    else return res;
}
double getDist(int i, int j)
{
    double dx = node[i].x - node[j].x;
    double dy = node[i].y - node[j].y;  
    return sqrt(dx*dx + dy*dy);
}

int main(){
    int t, n;
    cin >> t;
    while(t--){
        cin >> n;
        int cnt = 0;
        for(int i = 0; i < n; ++i) cin >> node[i].x >> node[i].y;
        for(int i = 0; i < n; ++i)
            for(int j = 0; j < n; ++j)
            {
                if(i != j)
                {
                    double dist = getDist(i, j);
                    if(dist <= 1000 && dist >= 10){
                        edge[cnt].from = i;
                        edge[cnt].to = j;
                        edge[cnt++].dist = dist*100;
                    }
                }
            }
        double tmpx = Kruskal(cnt, n);
        if(tmpx == -1) printf("oh!\n");
        else printf("%.1lf\n", tmpx);
    }
    return 0;
}