hpu暑假训练 【最小生成树解题思路以及模板】

/*给出n个点，要求距离小于10或大于1000不能建边，问联通这些点至少需要的距离 不存在输出-1 */#include<cstdio>#include<vector>#include<cmath>#include<algorithm>using namespace std;struct Dot{double x,y;}dot[105];double caculateDistance(const Dot a,const Dot b){return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));}struct Node{int p,q;double dis;bool friend operator < (Node a,Node b){return a.dis < b.dis;}};vector<Node> data;int f[105];//父节点 int find(int x){if (x != f[x])f[x] = find(f[x]);return f[x];}bool join(int x,int y){int fx = find(x);int fy = find(y);if (fx != fy){f[fx] = fy;return true;}return false;}int main(){int n;scanf ("%d",&n);for (int i = 1 ; i <= n ; i++)f[i] = i;for (int i = 1 ; i <= n ; i++)scanf ("%lf%lf",&dot[i].x,&dot[i].y);for (int i = 1 ; i <= n ; i++){for (int j = i+1 ; j <= n ; j++){double dis = caculateDistance(dot[i],dot[j]);if (dis >= 10 && dis <= 1000){Node t;t.p = i;t.q = j;t.dis = dis;data.push_back(t);}}}sort(data.begin(),data.end());int ant = 0;//已经连上的边 double ans = 0;for (int i = 0 ; i < data.size() ; i++){if (join(data[i].p,data[i].q)){ans += data[i].dis;ant++;}if (ant == n-1)//剪枝 break;}if (ant == n-1)printf ("%lf\n",ans);elseprintf ("-1\n");return 0;}