HDU 1865

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<math.h>
 4 #define maxn 10000005;
 5 int fa[maxn], sum[maxn];
 6 int ans;
 7 
 8 int find(int x){
 9     if(fa[x] == x)
10         return fa[x];
11     else
12         return fa[x];
13 }
14 
15 int main(){
16     int t;
17     while(scanf("%d", &t) != EOF){
18         if(t==0){
19             printf("1\n");
20             continue;
21         }
22         ans = 0;
23         for(int i = 1; i < maxn; i++){
24             sum[i]=1;
25             fa[i]=i;
26         }
27         int x,y;
28         while(t--){
29             scanf("%d%d",&x,&y);
30             int fa_x, fa_y;
31             fa_x = find( x );
32             fa_y = find( y );
33             if(sum[fa_x] < sum[fa_y]){
34                 fa[fa_x] = fa_y;
35                 sum[fa_y] += sum[fa_x ];
36                 ans = fmax(ans, sum[fa_y]);
37             }
38             else{
39                 fa[fa_y] = fa_x;
40                 sum[fa_x] += sum[fa_y];
41                 ans = fmax(ans, sum[fa_x]);
42             }
43         }
44         printf("%d\n",ans);
45     }
46     return 0;
47 }