hdu 1856 并查集（路径压缩）

 1 #include<cstdio>
 2 #include<cstring>
 3 
 4 int set[10000000 + 50];
 5 int sum[10000000 + 50];
 6 bool visit[10000000 + 50];
 7 
 8 int find(int x)
 9 {
10     int r = x;
11     while(set[r] != r)
12         r = set[r];
13     int i = x;
14     int j;
15     while(i != r)
16     {
17         j = set[i];
18         set[i] = r;
19         i = j;
20     }
21     return r;
22 }
23 
24 void merge(int a, int b)
25 {
26      int i = find(a);
27      int j = find(b);
28      if(i != j) set[i] = j;
29      visit[a] = visit[b] = true;
30      return ;
31 }
32 
33 int main()
34 {
35     int a,b,n;
36     while(~scanf("%d",&n))
37     {
38         if(n == 0)
39         {
40             printf("1\n");
41             continue;
42         }
43         for(int i = 1; i <= 10000000; i++)
44             set[i] = i;
45         for(int i = 0; i < n; i++)
46         {
47             scanf("%d%d",&a,&b);
48             merge(a,b);
49         }
50         for(int i = 1; i <= 10000000; i++)
51         {
52              if(visit[i])
53              {
54                  sum[find(i)]++;
55              }
56         }
57         int max = 0;
58         for(int i = 1; i <= 10000000; i++)
59         {
60             if(visit[i] && set[i] == i)
61             {
62                 if(sum[i] > max)
63                     max = sum[i];
64             }
65         }
66         printf("%d\n",max);
67         memset(visit,0,sizeof(visit));
68         memset(sum,0,sizeof(sum));
69     }
70     return 0;
71 }