5567번) 결혼식 - 그래프

문제 출처 : https://www.acmicpc.net/problem/5567

import java.util.HashSet; import java.util.Scanner; public class Q5567 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); sc.nextInt(); int num = sc.nextInt(); int[][] relationShip = new int[num][2]; HashSet<Integer> friendList = new HashSet<Integer>(); for ( int i = 0 ; i < num; i++ ) { int temp1 = sc.nextInt(); int temp2 = sc.nextInt(); if ( temp1 == 1 ) { friendList.add(temp2); num -= 1; i -= 1; } else { relationShip[i][0] = temp1; relationShip[i][1] = temp2; } } HashSet<Integer> friendOfFriendList = new HashSet<Integer>(); for ( int i = 0 ; i < num; i++ ) { int temp = relationShip[i][0]; if ( friendList.contains(temp) ) { //친구의 친구 friendOfFriendList.add(relationShip[i][1]); } temp = relationShip[i][1]; if ( friendList.contains(temp) ) { //친구의 친구 friendOfFriendList.add(relationShip[i][0]); } } friendList.addAll(friendOfFriendList); System.out.println(friendList.size()); } }