[자바 알고리즘 문제풀이] 뒤집어도 똑같은 문자열 / replaceAll()

24 Jun 2022 - 1 minute read

🔒 자바 알고리즘 문제풀이

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🔐 뒤집어도 똑같은 문자열 ☝

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대소문자에 관계없이 문자열을 앞뒤로 뒤집었을 때 같으면 SUCCESS, 다르면 FAIL을 출력해보자.

🔓 .charAt()

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import java.util.Scanner;

class Main {

    public String solution(String str){
        String answer = "SUCCESS";
        str = str.toUpperCase();
        int len = str.length();

        for (int i = 0; i < len / 2; i++) {
            if (str.charAt(i) != str.charAt(len - i - 1)) return "FAIL";
        }

        return answer;
    }

    public static void main(String[] args) {
        Main main = new Main();

        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();

        System.out.println(main.solution(str));
    }
}

🔓 StringBuilder()

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import java.util.Scanner;

class Main {

    public String solution(String str){
        String answer = "FAIL";
        String temp = new StringBuilder(str).reverse().toString();

        if (str.equalsIgnoreCase(temp)) answer = "SUCCESS";

        return answer;
    }

    public static void main(String[] args) {
        Main main = new Main();

        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();

        System.out.println(main.solution(str));
    }
}

출력결과

java
FAIL

ABcba
SUCCESS

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🔐 뒤집어도 똑같은 문자열 ✌

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숫자나 특수문자는 무시하고 알파벳만 따졌을 때, 대소문자에 관계없이 문자열을 앞뒤로 뒤집어서 같으면 SUCCESS, 다르면 FAIL을 출력해보자.

import java.util.Locale;
import java.util.Scanner;

class Main {

    public String solution(String str){
        String answer = "FAIL";
        str = str.toUpperCase().replaceAll("[^A-Z]", "");

        String tmp = new StringBuilder(str).reverse().toString();
        if (str.equals(tmp)) answer = "SUCCESS";

        return answer;
    }

    public static void main(String[] args) {
        Main main = new Main();

        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();

        System.out.println(main.solution(str));
    }
}

출력결과

A12$(#)BC459p5cba
SUCCESS

ab!2#4Bc
FAIL

🔑 .replaceAll()

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• String replaceAll(String regex, String replacement) : 첫번째 인자값 - 변환하고자 하는 대상, 두번째 인자값 - 변환할 문자 값

• Character classes

  • [abc] : a, b, or c (simple class)

  • [^abc] : Any character except a, b, or c (negation)

  • [a-zA-Z] : a through z or A through Z, inclusive (range)

  • [a-d[m-p]] : a through d, or m through p: [a-dm-p] (union)

  • [a-z&&[def]] : d, e, or f (intersection)

  • [a-z&&[^bc]] : a through z, except for b and c: [ad-z] (subtraction)

  • [a-z&&[^m-p]] : a through z, and not m through p: [a-lq-z](subtraction)