并查集应用类题目，关键是如何把题意转化成并查集问题

代码随想录

import java.util.Scanner;

public class Main{
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        int n = scanner.nextInt();
        DisJoint disjoint = new DisJoint(n+1);
        
        while(n-- > 0){
            int a = scanner.nextInt();
            int b = scanner.nextInt();
            if(disjoint.isSame(a, b)){
                System.out.println(a+" "+b);
                break;
            }else{
               disjoint.join(a, b); 
            }
        }
    }
}

class DisJoint{
    private int[] farther;
    
    public DisJoint(int N){
        farther = new int[N];
        for(int i = 0; i < N; i++){
            farther[i] = i;
        }
    }
    
    public int find(int n){
        if(n == farther[n]){
            return n;
        }else{
            return farther[n] = find(farther[n]);
        }
       // return n == farther[n] ? n : (farther[n] = find(farther[n]));
    }