1487：【例 2】北极通讯网络 - 题解

原题地址：点击这里

只需要找到最小生成树中第 k 大的边即可。

 1 #include<cstdio>
 2 #include<cmath>
 3 #include<algorithm>
 4 
 5 #define N 505
 6 #define M N*N*2
 7 #define K 105
 8 
 9 using namespace std;
10 
11 int n,m,k;
12 double ans=0;
13 
14 struct Valiant{
15     int x,y;
16 }P[N];
17 double dist(int a,int b)
18 {
19     int x1=P[a].x,y1=P[a].y;
20     int x2=P[b].x,y2=P[b].y;
21     return (double)sqrt((double)(x1-x2)*(x1-x2)+(double)(y1-y2)*(y1-y2));
22 }
23 
24 struct Allan{
25     int from,to;
26     double val;
27 }edge[M];
28 int edge_cnt=0;
29 int head[N];
30 void Add_edge(int from,int to,double value)
31 {
32     edge_cnt++;
33     edge[edge_cnt].from=from;
34     edge[edge_cnt].to=to;
35     edge[edge_cnt].val=value;
36     return;
37 }
38 
39 int Father[N];
40 void Union_init()
41 {
42     for(int i=1;i<=n;i++)
43         Father[i]=i;
44     return;
45 }
46 int Union_get(int x)
47 {
48     if(Father[x]==x) return x;
49     return Father[x]=Union_get(Father[x]);
50 }
51 
52 int Kruskal_cnt=0;
53 bool cmp(Allan x,Allan y)
54 {
55     return x.val<y.val;
56 }
57 void Kruskal()
58 {
59     sort(edge+1,edge+m+1,cmp);
60     Union_init();
61     for(int i=1;i<=m;i++)
62     {
63         int x=Union_get(edge[i].from);
64         int y=Union_get(edge[i].to);
65         if(x==y) continue;
66         Kruskal_cnt++;
67         Father[x]=y;
68         if(Kruskal_cnt>=n-k)
69         {
70             printf("%.2lf\n",edge[i].val);
71             return;
72         }
73     }
74     return;
75 }
76 
77 int main()
78 {
79     scanf("%d%d",&n,&k);
80     if(n==k)
81     {
82         printf("0\n");
83         return 0;
84     }
85     for(int i=1;i<=n;i++)
86         scanf("%d%d",&P[i].x,&P[i].y);
87     for(int i=1;i<=n;i++)
88         for(int j=1;j<=n;j++)
89         {
90             if(i==j) continue;
91             Add_edge(i,j,dist(i,j));
92             Add_edge(j,i,dist(i,j));
93         }
94     m=edge_cnt;
95     Kruskal();
96     return 0;
97 }

标签：cnt,return,北极,int,题解,edge,1487,double,y1
来源： https://www.cnblogs.com/jerrycyx/p/16439793.html