题目链接
1 /*
2 Name:HDU-1232-畅通工程
3 Copyright:
4 Author:
5 Date: 2018/4/12 15:38:11
6 Description:
7 并查集模板题
8 */
9 #include <iostream>
10 #include <vector>
11 #include <algorithm>
12 using namespace std;
13 struct DisjoinSet {
14 vector<int> father, rank;
15
16 DisjoinSet(int n): father(n), rank(n) {
17 for (int i=0; i<n; i++) {
18 father[i] = i;
19 }
20 }
21
22 int find(int v) {
23 return father[v] = father[v] == v? v:find(father[v]);
24 }
25
26 void merge(int x, int y) {
27 int a = find(x), b = find(y);
28 if (rank[a] < rank[b]) {
29 father[a] = b;
30 } else {
31 father[b] = a;
32 if (rank[b] == rank[a]) {
33 ++rank[a];
34 }
35 }
36 }
37 } ;
38 int main()
39 {
40 int n, m;
41 while (cin>>n>>m) {
42 DisjoinSet msf(1000+5);
43 for (int i=0; i<m; i++) {
44 int a,b;
45 cin>>a>>b;
46 msf.merge(a,b);
47 }
48 int ans = 0;
49 for(int i=1; i<=n; i++){
50 if(msf.father[i]==i) ans++;
51 }
52 cout<<ans-1<<endl;
53 }
54 return 0;
55 }
