[백준 1822] 차집합 - JAVA

https://www.acmicpc.net/problem/1822

 

s1 순회하며 s2에 없으면 정답에 포함

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

class Main {

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    br.readLine();

    Set<Integer> s1 = new HashSet<>();
    Set<Integer> s2 = new HashSet<>();

    Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).forEach(s1::add);
    Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).forEach(s2::add);

    List<Integer> l = new ArrayList<>();

    for (int e1 : s1) {
      if (!s2.contains(e1)) {
        l.add(e1);
      }
    }

    StringBuilder sb = new StringBuilder(l.size() + "\n");
    l.stream().sorted().forEach(e -> sb.append(e).append(" "));
    System.out.println(sb);
  }
}