8. 유효한 팰린드롬

import java.util.*;

class Main {
	public String solution(String str) {
		String answer = "YES";
		str = str.toUpperCase();
		int lt = 0, rt = str.length() - 1;

		while (lt < rt) {
			if (!Character.isAlphabetic(str.charAt(lt))) {
				lt++;
			} else if (!Character.isAlphabetic(str.charAt(rt))) {
				rt--;
			} else if (str.charAt(lt) != str.charAt(rt)) {
				answer = "NO";
				break;
			} else {
				lt++;
				rt--;
			}
		}
		return answer;
	}

	public static void main(String[] args) {
		Main T = new Main();
		Scanner kb = new Scanner(System.in);
		System.out.println(T.solution(kb.nextLine()));
	}
}

 

 

import java.util.*;

class Main {
	public String solution(String str) {
		String answer = "NO";
		str = str.toUpperCase().replaceAll("[^A-Z]", "");
		String tmp = new StringBuilder(str).reverse().toString();
		if(str.equals(tmp))
			answer = "YES";
		return answer;
	}

	public static void main(String[] args) {
		Main T = new Main();
		Scanner kb = new Scanner(System.in);
		System.out.println(T.solution(kb.nextLine()));
	}
}

replaceAll("정규식", "")