Day 06 - 코딩테스트 입문(Java)

1. 문자열 뒤집기

https://school.programmers.co.kr/learn/courses/30/lessons/120822

프로그래머스

▼ 방법 1

class Solution {
    public String solution(String my_string) {
        String answer = "";
        
        for(int i = my_string.length() - 1; i >= 0; i--) {
            answer += my_string.charAt(i);
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public String solution(String my_string) {
        String answer = "";
        StringBuilder sb = new StringBuilder();
        
        answer = sb.append(my_string).reverse().toString();
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public String solution(String my_string) {
        String answer = "";
        
        answer = new StringBuilder(my_string).reverse().toString();
        
        return answer;
    }
}

 

2. 직각삼각형 출력하기

https://school.programmers.co.kr/learn/courses/30/lessons/120823

프로그래머스

▼ 방법 1

import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        
        for(int i = 0; i < n; i++) {
            for(int j = 0; j <= i; j++) {
                System.out.print("*");
            }
            
            System.out.println();
        }
    }
}

 

▼ 방법 2

import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        
        for(int i = 1; i <= n; i++) {
            System.out.println("*".repeat(i));
        }
    }
}

 

3. 짝수 홀수 개수

https://school.programmers.co.kr/learn/courses/30/lessons/120824

프로그래머스

▼ 방법 1

class Solution {
    public int[] solution(int[] num_list) {
        int[] answer = new int[2];
        
        for(int num : num_list) {
            if(num % 2 == 0) {
                answer[0]++;
            } else {
                answer[1]++;
            }
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int[] solution(int[] num_list) {
        int[] answer = new int[2];
        
        for(int i = 0; i < num_list.length; i++) {
            answer[num_list[i] % 2]++;
        }
        
        return answer;
    }
}

 

▼ 방법 3

import java.util.stream.IntStream;
import java.util.Arrays;

class Solution {
    public int[] solution(int[] num_list) {
        int[] answer = {};
        
        answer = IntStream.of((int) Arrays.stream(num_list).filter(i -> i % 2 == 0).count(), (int) Arrays.stream(num_list).filter(i -> i % 2 == 1).count()).toArray();
        
        return answer;
    }
}

 

4. 문자 반복 출력하기

https://school.programmers.co.kr/learn/courses/30/lessons/120825

프로그래머스

▼ 방법 1

class Solution {
    public String solution(String my_string, int n) {
        String answer = "";
        
        for(String s : my_string.split("")) {
            answer += s.repeat(n);
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public String solution(String my_string, int n) {
        String answer = "";
        
        for(char c : my_string.toCharArray()) {
            answer += String.valueOf(c).repeat(n);
        }
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public String solution(String my_string, int n) {
        String answer = "";
        
        for(char c : my_string.toCharArray()) {
            answer += ("" + c).repeat(n);
        }
        
        return answer;
    }
}