本文已参与「新人创作礼」活动，一起开启掘金创作之路。

一、并查集

并查集优秀学习文章.

二、题目

P1551亲戚

import java.util.*;

public class Main{
    
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        String[] strArr = str.split(" ");
        int n = Integer.parseInt(strArr[0]);
        int m = Integer.parseInt(strArr[1]);
        int p = Integer.parseInt(strArr[2]);
        
        DisJointSet djs = new DisJointSet();
        djs.init(n);
        for (int i = 0; i < m; i++) {
            String str1 = sc.nextLine();
            String[] strArr1 = str1.split(" ");
            int x = Integer.parseInt(strArr1[0]);
            int y = Integer.parseInt(strArr1[1]);
            
            djs.merge(x,y);
        }
        
        for (int i = 0; i < p; i++) {
            String str2 = sc.nextLine();
            String[] strArr2 = str2.split(" ");
            int x = Integer.parseInt(strArr2[0]);
            int y = Integer.parseInt(strArr2[1]);
        
            int res1 = djs.find(x);
            int res2 = djs.find(y);
            if (res1 == res2) {
                System.out.println("Yes");
            }else {
                System.out.println("No");
            }
        }
    }
}

class DisJointSet{
        int[] parent;
        int[] rank;
        
        public void init(int n) {
            parent = new int[n + 1];
            rank = new int[n + 1];
            for (int i = 1; i <= n; i++) {
                parent[i] = i;
                rank[i] = 1;
            }
        }
        
        public int find(int x) {
            if (x == parent[x]) {
                return x;
            }else {
                parent[x] = find(parent[x]);
                return parent[x];
            }
        }
        
        public void merge(int x, int y) {
            int rx = find(x);
            int ry = find(y);
            
            if (rx != ry) {
                if (rank[rx] < rank[ry]) {
                    swap(rx,ry);
                }
                parent[ry] = rx;
                
                if (rank[rx] == rank[ry]) {
                    rank[rx]++;
                }
            }
        }
        
        public void swap(int x, int y) {
            int temp = x;
            x = y;
            y = temp;
        }
    }

P1536村村通.

200.岛屿的数量.

684.冗余连接.