Day 13. 코딩 기초 트레이닝(Java)

1. n 번째 원소부터

https://school.programmers.co.kr/learn/courses/30/lessons/181892

프로그래머스

▼ 방법 1

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

 

▼ 방법 2

import java.util.Arrays;

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = {};
        
        answer = Arrays.copyOfRange(num_list, n - 1, num_list.length);
        
        return answer;
    }
}

 

2. 순서 바꾸기

https://school.programmers.co.kr/learn/courses/30/lessons/181891

프로그래머스

▼ 방법 1

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

 

▼ 방법 2

import java.util.stream.IntStream;

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = {};
        
        answer = IntStream.range(0, num_list.length).map(i -> num_list[(i + n) % num_list.length]).toArray();
        
        return answer;
    }
}

 

3. 왼쪽 오른쪽

https://school.programmers.co.kr/learn/courses/30/lessons/181890

프로그래머스

import java.util.Arrays;

class Solution {
    public String[] solution(String[] str_list) {
        String[] answer = {};
        
        for(int i = 0; i < str_list.length; i++) {
            if(str_list[i].equals("l")) {
                answer = Arrays.copyOfRange(str_list, 0, i);
                
                break;
            } else if(str_list[i].equals("r")) {
                answer = Arrays.copyOfRange(str_list, i + 1, str_list.length);
                
                break;
            }
        }
        
        return answer;
    }
}

 

4. n 번째 원소까지

https://school.programmers.co.kr/learn/courses/30/lessons/181889

프로그래머스

▼ 방법 1

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = new int[n];
        
        for(int i = 0; i < n; i++) {
            answer[i] = num_list[i];
        }
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.Arrays;

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = {};
        
        answer = Arrays.copyOfRange(num_list, 0, n);
        
        return answer;
    }
}

 

▼ 방법 3

import java.util.Arrays;

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = {};
        
        answer = Arrays.stream(num_list).limit(n).toArray();
        
        return answer;
    }
}

 

5. n개 간격의 원소들

https://school.programmers.co.kr/learn/courses/30/lessons/181888

프로그래머스

▼ 방법 1

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = new int[num_list.length % n == 0 ? num_list.length / n : num_list.length / n + 1];
        int idx = 0;
        
        for(int i = 0; i < num_list.length; i += n) {
            answer[idx++] = num_list[i];
        }
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.stream.IntStream;

class Solution {
    public int[] solution(int[] num_list, int n) {
        int[] answer = {};
        
        answer = IntStream.range(0, (num_list.length - 1) / n + 1).map(i -> num_list[i * n]).toArray();
        
        return answer;
    }
}