Day 14 - 코딩테스트 입문(Java)

1. 가까운 수

https://school.programmers.co.kr/learn/courses/30/lessons/120890

프로그래머스

import java.util.Arrays;

class Solution {
    public int solution(int[] array, int n) {
        int answer = 0;
        int minIdx = 0;
        
        Arrays.sort(array);
        
        for(int i = 0; i < array.length; i++) {
            if(Math.abs(n - array[minIdx]) > Math.abs(n - array[i])) {
                minIdx = i;
            }
        }
        
        answer = array[minIdx];
        
        return answer;
    }
}

 

2. 369게임

https://school.programmers.co.kr/learn/courses/30/lessons/120891

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int order) {
        int answer = 0;
        
        while(order > 0) {
            if(order % 10 == 3 || order % 10 == 6 || order % 10 == 9) {
                answer++;
            }
            
            order = order / 10;
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(int order) {
        int answer = 0;
        
        for(char c : String.valueOf(order).toCharArray()) {
            if(c == '3' || c == '6' || c == '9') {
                answer++;
            }
        }
        
        return answer;
    }
}

 

▼ 방법 3

import java.util.Arrays;

class Solution {
    public int solution(int order) {
        int answer = 0;
        
        answer = (int) Arrays.stream(String.valueOf(order).split("")).map(Integer::parseInt).filter(i -> i == 3 || i == 6 || i == 9).count();
        
        return answer;
    }
}

 

3. 암호 해독

https://school.programmers.co.kr/learn/courses/30/lessons/120892

프로그래머스

▼ 방법 1

class Solution {
    public String solution(String cipher, int code) {
        String answer = "";
        
        for(int i = code - 1; i < cipher.length(); i += code) {
            answer += cipher.charAt(i);
        }
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.stream.IntStream;
import java.util.stream.Collectors;

class Solution {
    public String solution(String cipher, int code) {
        String answer = "";
        
        answer = IntStream.range(0, cipher.length()).filter(i -> i % code == code - 1).mapToObj(j -> String.valueOf(cipher.charAt(j))).collect(Collectors.joining());
        
        return answer;
    }
}

 

4. 대문자와 소문자

https://school.programmers.co.kr/learn/courses/30/lessons/120893

프로그래머스

▼ 방법 1

class Solution {
    public String solution(String my_string) {
        String answer = "";
        
        for(char c : my_string.toCharArray()) {
            if(Character.isLowerCase(c)) {
                answer += Character.toUpperCase(c);
            } else {
                answer += Character.toLowerCase(c);
            }
        }
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.stream.Collectors;

class Solution {
    public String solution(String my_string) {
        String answer = "";
        
        answer = my_string.chars().mapToObj(c -> String.valueOf((char) (Character.isLowerCase(c) ? Character.toUpperCase(c) : Character.toLowerCase(c)))).collect(Collectors.joining());
        
        return answer;
    }
}