[Java] 회문 문자열

- 앞에서 읽을 때, 뒤에서 읽을 때나 같은 문자열 => 회문 문자열

 

(입력)

Moon
gooG

 

(출력)

 

# subString, equalsIgnoreCase 사용

public class Main {
    private String solution(String s) {
        String answer = "YES";

        for (int i=0; i<s.length()/2; i++) {
            if (!s.substring(i, i+1).equalsIgnoreCase(s.substring(s.length()-i-1, s.length()-i))) {
                return "NO";
            }
        }

        return answer;
    }

    public static void main(String[] args) {
        Main T = new Main();
        System.out.println(T.solution("Moon"));
        System.out.println(T.solution("gooG"));
    }
}

 

# toUpperCase, charAt 사용

public class Main {
    private String solution(String s) {
        String answer = "YES";
        s = s.toUpperCase();

        for (int i=0; i<s.length()/2; i++) {
            if (s.charAt(i) != s.charAt(s.length()-i-1)) {
                return "NO";
            }
        }

        return answer;
    }

    public static void main(String[] args) {
        Main T = new Main();
        System.out.println(T.solution("Moon"));
        System.out.println(T.solution("gooG"));
    }
}

 

# StringBuffer, reverse, equalsIgnoreCase 사용

public class Main {
    private String solution(String s) {
        String answer = "NO";
        String reversedS = new StringBuffer(s).reverse().toString();

        if (s.equalsIgnoreCase(reversedS)) answer = "YES";

        return answer;
    }

    public static void main(String[] args) {
        Main T = new Main();
        System.out.println(T.solution("Moon"));
        System.out.println(T.solution("gooG"));
    }
}

 

# StringBuilder, reverse, equalsIgnoreCase 사용

public class Main {
    private String solution(String s) {
        String answer = "NO";
        String reversedS = new StringBuilder(s).reverse().toString();

        if (s.equalsIgnoreCase(reversedS)) answer = "YES";

        return answer;
    }

    public static void main(String[] args) {
        Main T = new Main();
        System.out.println(T.solution("Moon"));
        System.out.println(T.solution("gooG"));
    }
}

 

# String -> char[] -> List 로 변환 후 Collections.reverse, Collectors.joining() 사용

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
    private String solution(String s) {
        String answer = "NO";
        char[] arr = s.toCharArray(); // String -> char[]
        List<Character> list = new ArrayList<>();
        for (char c: arr) { // char[] -> List
            list.add(c);
        }

        Collections.reverse(list);
        if (list.stream() // Stream<Character>
                .map(String::valueOf) // Stream<String>
                .collect(Collectors.joining())
                .equalsIgnoreCase(s)) 
            answer = "YES";

        return answer;
    }

    public static void main(String[] args) {
        Main T = new Main();
        System.out.println(T.solution("Moon"));
        System.out.println(T.solution("gooG"));
    }
}