Day 18 - 코딩테스트 입문(Java)

1. 문자열안에 문자열

https://school.programmers.co.kr/learn/courses/30/lessons/120908

프로그래머스

▼ 방법 1

class Solution {
    public int solution(String str1, String str2) {
        int answer = 0;
        
        answer = str1.contains(str2) ? 1 : 2;
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(String str1, String str2) {
        int answer = 0;
        
        answer = str1.indexOf(str2) == -1 ? 2 : 1;
        
        return answer;
    }
}

 

2. 제곱수 판별하기

https://school.programmers.co.kr/learn/courses/30/lessons/120909

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int n) {
        int answer = 0;
        
        answer = n % Math.sqrt(n) == 0 ? 1 : 2;
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(int n) {
        int answer = 0;
        
        answer = Math.sqrt(n) % 1 == 0 ? 1 : 2;
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public int solution(int n) {
        int answer = 0;
        
        answer = Math.sqrt(n) == Math.floor(Math.sqrt(n)) ? 1 : 2;
        
        return answer;
    }
}

 

▼ 방법 4

class Solution {
    public int solution(int n) {
        int answer = 0;
        
        answer = (int) Math.sqrt(n) * Math.sqrt(n) == n ? 1 : 2;
        
        return answer;
    }
}

Math.sqrt() : 자바에서 특정값의 제곱근(루트)을 구할 때 사용

 

▼ 방법 5

class Solution {
    public int solution(int n) {
        int answer = 2;
        
        for(int i = 1; i < n; i++) {
            if(Math.pow(i, 2) == n) {
                answer = 1;
                
                break;
            }
        }
        
        return answer;
    }
}

 

3. 세균 증식

https://school.programmers.co.kr/learn/courses/30/lessons/120910

프로그래머스

▼ 방법 1

class Solution {
    public int solution(int n, int t) {
        int answer = n;
        
        for(int i = 1; i <= t; i++) {
            answer *= 2;
        }
        
        return answer;
    }
}

 

▼ 방법 2

class Solution {
    public int solution(int n, int t) {
        int answer = 0;
        
        answer = n * (int) Math.pow(2, t);
        
        return answer;
    }
}

 

▼ 방법 3

class Solution {
    public int solution(int n, int t) {
        int answer = 0;
        
        answer = n << t;
        
        return answer;
    }
}

 

4. 문자열 정렬하기 (2)

https://school.programmers.co.kr/learn/courses/30/lessons/120911

프로그래머스

▼ 방법 1

import java.util.Arrays;

class Solution {
    public String solution(String my_string) {
        String answer = "";
        char[] c = my_string.toLowerCase().toCharArray();
        
        Arrays.sort(c);
        
        answer = new String(c);
        
        return answer;
    }
}

 

▼ 방법 2

import java.util.Arrays;

class Solution {
    public String solution(String my_string) {
        String answer = "";
        char[] c = my_string.toLowerCase().toCharArray();
        
        Arrays.sort(c);
        
        answer = String.valueOf(c);
        
        return answer;
    }
}

 

▼ 방법 3

import java.util.Arrays;

class Solution {
    public String solution(String my_string) {
        String answer = "";
        String[] s = my_string.toLowerCase().split("");
        
        Arrays.sort(s);
        
        answer = String.join("", s);
        
        return answer;
    }
}

 

▼ 방법 4

import java.util.stream.Collectors;

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