【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[1005];

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 = 1 ; 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 = 0 ; i < op_n; ++ i) {
            int x, y; cin >> x >> y;
            Union(x, y);
        }
        int cnt = 0;
        for (int i = 1; i <= n; ++ i) {
            if (father[i] == i) {
                cnt ++;
            }
        }
        cout << cnt << endl;
    }
    return 0;
}

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());
        }
    }
}