【HDU1231】How Many Tables（并查集基础题）

什么也不用说，并查集裸题，直接盲敲即可。

 #include <iostream>
 #include <cstring>
 #include <cstdlib>
 #include <cstdio>
 #include <cctype>
 #include <cmath>
 #include <algorithm>
 #include <numeric>
 using namespace std;

 int father[];

 int getFather (int x) {
     if (x != father[x]) {
         father[x] = getFather(father[x]);
     }
     return father[x];
 }

 void Union (int p, int q) {
     int x = getFather (p);
     int y = getFather (q);
     if (x != y) {
         father[y] = x;
     }
 }

 void Init (int n) {
     for (int i =  ; i <= n; ++ i) {
         father[i] = i;
     }
 }

 int main () {
     int T; cin >> T;
     while (T --) {
         int n, op_n;
         cin >> n >> op_n;
         Init(n);
         for (int i =  ; i < op_n; ++ i) {
             int x, y; cin >> x >> y;
             Union(x, y);
         }
         int cnt = ;
         for (int i = ; i <= n; ++ i) {
             if (father[i] == i) {
                 cnt ++;
             }
         }
         cout << cnt << endl;
     }
     return ;
 }

 import java.util.*;
 import java.io.*;
 import java.math.*;

 class DisjointSet{
     public static int MAXX = 1005;
     public int ans = 0;
     public int father[] = new int[MAXX];
     public int vis[] = new int[MAXX];

     public DisjointSet(){
         this.ans = 0;
     }

     public int GetAns(){
         return ans;
     }
     public int GetFather(int x){
         if(father[x] != 0){
             return GetFather(father[x]);
         }
         else{
             return x;
         }
     }

     public void Union(int x, int y){
         int fx = GetFather(x);
         int fy = GetFather(y);
         if(fx != fy){
             father[fy] = fx;
             ans++;
         }
     }
 }

 public class Main{
     public static void main(String args[]){
         Scanner in = new Scanner(System.in);
         int l = in.nextInt();
         int a, b, n, opn;
         for(int i = 0; i < l; i++){
             n = in.nextInt();
             DisjointSet D = new DisjointSet();
             opn = in.nextInt();
             for(int j = 0; j < opn; j++){
                 a = in.nextInt();
                 b = in.nextInt();
                 D.Union(a, b);
             }
             System.out.println(n - D.GetAns());
         }
     }
 }