[JAVA] 배열 뒤집기(세 가지 방법)

1. 기본 for문 ( ++ )

class Solution {
    public int[] solution(int[] num_list) {
        int[] answer = new int[num_list.length];
        
        for(int i=0;i<num_list.length;i++) {
            answer[num_list.length-1-i] = num_list[i];
        }
        return answer;
    }
}

2. 기본 for문 ( -- )

class Solution {
    public int[] solution(int[] num_list) {
        int[] answer = new int[num_list.length];
        int startIdx = 0;
        
        for(int i= num_list.length-1; i>=0; i--) {
            answer[startIdx] = num_list[i];
            startIdx++;
        }
        return answer;
    }
}

3. Collections.reverse 

import java.util.Collections;
import java.util.stream.Collectors;
import java.util.Arrays;
import java.util.List;

class Solution {
    public int[] solution(int[] num_list) {
		// int[ ] => list
        List<Integer> list = Arrays.stream(num_list).boxed().collect(Collectors.toList());
      
        Collections.reverse(list);
        
        // list => int[ ]
        return list.stream().mapToInt(Integer::intValue).toArray();
    
    }
}

배열 뒤집기 알고리즘 나중에 유용할 것 같아 따로 모아두기..!