1 #include <cstdio>
 2 #include <cstring>
 3 using namespace std;
 4 int n, m;
 5 int G[1005][1005];
 6 int vis[1005];     //标记数组
 7 int is[1005];      //有道路连接的点
 8 
 9 void dfs(int u){
10     if(vis[u]) return;   //被访问过就进行回溯
11     vis[u] = 1;          //标记
12     for(int i = 1; i <= 1000; i++){
13         if(G[u][i]) dfs(i);    
14     }
15 }
16 
17 int main(){
18     int u, v;
19     while(~scanf("%d", &n) && n){
20         scanf("%d", &m);
21         memset(G, 0, sizeof(G));
22         memset(vis, 0, sizeof(vis));
23         memset(is, 0, sizeof(is));
24 
25         for(int i = 0; i < m; i++){
26             scanf("%d%d", &u, &v);
27             G[u][v] = G[v][u] = 1;   //双向的路
28             is[u] = is[v] = 1;       
29         }
30 
31         int cnt = 0;     //计数
32         for(int i = 1; i <= n; i++){
33             if(is[i] && !vis[i]){   //有道路连接并且没被访问过
34                 dfs(i);   //进行搜索
35                 cnt++;   
36             }
37         }
38 
39         for(int i = 1; i <= n; i++){
40             if(!vis[i]) cnt++;      //统计独立的点
41         }
42 
43         printf("%d\n", cnt-1);
44     }
45     return 0;
46 }

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <vector>
 4 using namespace std;
 5 int n, m;
 6 vector<int> G[1005];   //邻接表
 7 int vis[1005];     //标记数组
 8 int is[1005];      //有道路连接的点
 9 
10 void dfs(int u){
11     if(vis[u]) return;   //被访问过就进行回溯
12     vis[u] = 1;          //标记
13     for(int i = 0; i < G[u].size(); i++) dfs(G[u][i]);
14 }
15 
16 int main(){
17     int u, v;
18     while(~scanf("%d", &n) && n){
19         scanf("%d", &m);
20         for(int i = 0; i < 1005; i++){
21             G[i].clear();
22         }
23         memset(vis, 0, sizeof(vis));
24         memset(is, 0, sizeof(is));
25 
26         for(int i = 0; i < m; i++){
27             scanf("%d%d", &u, &v);
28             G[u].push_back(v);
29             G[v].push_back(u);   //双向的路
30             is[u] = is[v] = 1;
31         }
32 
33         int cnt = 0;     //计数
34         for(int i = 1; i <= n; i++){
35             if(is[i] && !vis[i]){   //有道路连接并且没被访问过
36                 dfs(i);   //进行搜索
37                 cnt++;
38             }
39         }
40 
41         for(int i = 1; i <= n; i++){
42             if(!vis[i]) cnt++;      //统计独立的点
43         }
44 
45         printf("%d\n", cnt-1);
46     }
47     return 0;
48 }

 1 #include <cstdio>
 2 #include <cstring>
 3 using namespace std;
 4 int road[1005];
 5 
 6 int fd(int u){
 7     int r = u;
 8     while(road[r] != r){
 9         r = road[r];     //查
10     }
11 
12     int i = u;
13     int next;
14     while(i != r){      //状态压缩
15         next = road[i];
16         road[i] = r;
17         i = next;
18     }
19     return r;
20 }
21 
22 int main(){
23     int n;
24     while(scanf("%d", &n) == 1 && n){
25         int m;
26         scanf("%d", &m);
27         memset(road, 0, sizeof(road));
28         for(int i = 1; i <= n; i++){
29             road[i] = i;    //初始化并查集数组
30         }
31 
32         int a, b;
33         int a1, b1;
34         while(m--){
35             scanf("%d%d", &a, &b);
36             a1 = fd(a);    //查
37             b1 = fd(b);
38             if(a1 != b1){   //不属于同一个集合就并
39                 road[a1] = b1;
40             }
41         }
42 
43         int cnt = 0;
44         for(int i = 1; i <= n; i++){
45             if(road[i] == i) cnt++;
46         }
47 
48         printf("%d\n", cnt-1);
49     }
50     return 0;
51 }