PROGRAMMERES Level 1 스택/큐 같은 숫자는 싫어 (JAVA 자바)

import java.util.*;

public class Solution {
    public int[] solution(int []arr) {

        ArrayList<Integer> ar = new ArrayList<>();
        ar.add(arr[0]);
        int a = arr[0];
        
        for(int i=1; i<arr.length; i++){
            if(a != arr[i]) ar.add(arr[i]);
            a = arr[i];
        }
        
        int[] answer = new int[ar.size()];
        int c =0;
        
        for(int h : ar){
            answer[c] = h;
            c++;
        }
        
        return answer;
    }
}