Day 14. 코딩 기초 트레이닝(Java)

1. 홀수 vs 짝수

https://school.programmers.co.kr/learn/courses/30/lessons/181887

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int[] num_list) {
        int answer = 0;
        int odd = 0;
        int even = 0;
        
        for(int i = 1; i <= num_list.length; i++) {
            if(i % 2 == 1) {
                odd += num_list[i - 1];
            } else {
                even += num_list[i - 1];
            }
        }
        
        answer = Math.max(odd, even);
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.stream.IntStream;

class Solution {
    public int solution(int[] num_list) {
        int answer = 0;
        
        answer = Math.max(
            IntStream.iterate(0, i -> i < num_list.length, i -> i + 2).map(i -> num_list[i]).sum(),
            IntStream.iterate(1, i -> i < num_list.length, i -> i + 2).map(i -> num_list[i]).sum()
        );
        
        return answer;
    }
}

 

2. 5명씩

https://school.programmers.co.kr/learn/courses/30/lessons/181886

프로그래머스

▼ 방법 1

class Solution {
    public String[] solution(String[] names) {
        String[] answer = new String[names.length % 5 == 0 ? names.length / 5 : names.length / 5 + 1];
        int idx = 0;
        
        for(int i = 0; i < names.length; i += 5) {
            answer[idx++] = names[i];
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public String[] solution(String[] names) {
        String[] answer = new String[(names.length - 1) / 5 + 1];
        
        for(int i = 0; i < answer.length; i++) {
            answer[i] = names[5 * i];
        }
        
        return answer;
    }
}

 

3. 할 일 목록

https://school.programmers.co.kr/learn/courses/30/lessons/181885

프로그래머스

▼ 방법 1

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

class Solution {
    public String[] solution(String[] todo_list, boolean[] finished) {
        String[] answer = {};
        List<String> answerList = new ArrayList<>();
        
        for(int i = 0; i < finished.length; i++) {
            if(!finished[i]) {
                answerList.add(todo_list[i]);
            }
        }
        
        answer = answerList.toArray(String[]::new);
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.stream.IntStream;

class Solution {
    public String[] solution(String[] todo_list, boolean[] finished) {
        String[] answer = {};
        
        answer = IntStream.range(0, finished.length).filter(i -> !finished[i]).mapToObj(i -> todo_list[i]).toArray(String[]::new);
        
        return answer;
    }
}

 

4. n보다 커질 때까지 더하기

https://school.programmers.co.kr/learn/courses/30/lessons/181884

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int[] numbers, int n) {
        int answer = 0;
        
        for(int number : numbers) {
            answer += number;
            
            if(n < answer) {
                break;
            }
        }
        
        return answer;
    }
}

 

▼ 방법 2

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

 

5. 수열과 구간 쿼리 1

https://school.programmers.co.kr/learn/courses/30/lessons/181883

프로그래머스

class Solution {
    public int[] solution(int[] arr, int[][] queries) {
        int[] answer = arr.clone();
        
        for(int[] query : queries) {
            int s = query[0], e = query[1];
            
            for(int i = s; i <= e; i++) {
                answer[i]++;
            }
        }
        
        return answer;
    }
}