C++之路进阶——并查集（部落划分）

 1 #include<cstdio>
 2 #include<cmath>
 3 #include<iostream>
 4 #include<algorithm>
 5 #define maxn 1010
 6  
 7 using namespace std;
 8  
 9 int fa[maxn],n,m,cnt=0;
10  
11 struct ss
12    {
13      int x;
14      int y;
15    }e[maxn];
16     
17 struct node
18    {
19      int u;
20      int v;
21      int w;
22    }s[maxn*maxn];
23  
24 int find(int x)
25    {
26      if (fa[x]==x) return x;
27      fa[x]=find(fa[x]);
28      return fa[x];
29    }
30    
31 bool cmp(node a,node b)  
32    {
33      return a.w<b.w; 
34    }
35     
36 int main()
37    {
38      scanf("%d%d",&n,&m);   
39      for (int i=1;i<=n;i++)
40         scanf("%d%d",&e[i].x,&e[i].y);
41      for (int i=1;i<=n;i++)
42          for (int j=i+1;j<=n;j++)   
43             {
44                 cnt=cnt+1; 
45                 s[cnt].u=i;
46                 s[cnt].v=j;
47                 s[cnt].w=(e[j].x-e[i].x)*(e[j].x-e[i].x)+(e[j].y-e[i].y)*(e[j].y-e[i].y);
48             }
49     sort(s+1,s+cnt+1,cmp);
50     int k=n;
51     for (int i=1;i<=n;i++) fa[i]=i;
52     for (int i=1;i<=cnt;i++)
53        {
54          int fa1=find(s[i].u),fa2=find(s[i].v);
55          if (fa1!=fa2) k--;
56             fa[fa1]=fa2;
57             if (k<m) {printf("%0.2lf\n",sqrt(s[i].w));return 0;}     
58         }   
59    }