【HDU1231】How Many Tables（并查集基础题）

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdlib>
 4 #include <cstdio>
 5 #include <cctype>
 6 #include <cmath>
 7 #include <algorithm>
 8 #include <numeric>
 9 using namespace std;
10 
11 int father[1005];
12 
13 int getFather (int x) {
14     if (x != father[x]) {
15         father[x] = getFather(father[x]);
16     }
17     return father[x];
18 }
19 
20 void Union (int p, int q) {
21     int x = getFather (p);
22     int y = getFather (q);
23     if (x != y) {
24         father[y] = x;
25     }
26 }
27 
28 void Init (int n) {
29     for (int i = 1 ; i <= n; ++ i) {
30         father[i] = i;
31     }
32 }
33 
34 int main () {
35     int T; cin >> T;
36     while (T --) {
37         int n, op_n;
38         cin >> n >> op_n;
39         Init(n);
40         for (int i = 0 ; i < op_n; ++ i) {
41             int x, y; cin >> x >> y;
42             Union(x, y);
43         }
44         int cnt = 0;
45         for (int i = 1; i <= n; ++ i) {
46             if (father[i] == i) {
47                 cnt ++;
48             }
49         }
50         cout << cnt << endl;
51     }
52     return 0;
53 }

 1 import java.util.*;
 2 import java.io.*;
 3 import java.math.*;
 4 
 5 class DisjointSet{
 6     public static int MAXX = 1005;
 7     public int ans = 0;
 8     public int father[] = new int[MAXX];
 9     public int vis[] = new int[MAXX];
10     
11     public DisjointSet(){
12         this.ans = 0;
13     }
14     
15     public int GetAns(){
16         return ans;
17     }
18     public int GetFather(int x){
19         if(father[x] != 0){
20             return GetFather(father[x]);
21         }
22         else{
23             return x;
24         }
25     }
26     
27     public void Union(int x, int y){
28         int fx = GetFather(x);
29         int fy = GetFather(y);
30         if(fx != fy){
31             father[fy] = fx;
32             ans++;
33         }
34     }
35 }
36 
37 public class Main{
38     public static void main(String args[]){
39         Scanner in = new Scanner(System.in);
40         int l = in.nextInt();
41         int a, b, n, opn;
42         for(int i = 0; i < l; i++){
43             n = in.nextInt();
44             DisjointSet D = new DisjointSet();
45             opn = in.nextInt();
46             for(int j = 0; j < opn; j++){
47                 a = in.nextInt();
48                 b = in.nextInt();
49                 D.Union(a, b);
50             }
51             System.out.println(n - D.GetAns());
52         }
53     }
54 }