[알고리즘] 빈 배열에 추가, 삭제하기 Java

 

import java.util.ArrayList;
import java.util.List;

class Solution {
    public int[] solution(int[] arr, boolean[] flag) {
        List<Integer> answer = new ArrayList<>();
        for (int i = 0; i < flag.length; i++) {
          if (flag[i]) {
            for (int j = 0; j < arr[i] * 2; j++) {
              answer.add(arr[i]);
            }
          } else {
            for (int j = 0; j < arr[i]; j++) {
              answer.remove(answer.size()-1);
            }
          }
        }
        return answer.stream().mapToInt(Integer::intValue).toArray();
    }
}