Method palin

Java/Leetcode/Leetcode680.java:28–42

(StringBuilder s)

    static boolean palin(StringBuilder s) {
        StringBuilder s1 = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = Character.toLowerCase(s.charAt(i));
            if (ch >= 97 && ch <= 122 || ch >= 48 && ch <= 57) {
                s1.append(ch);
            }
        }

        StringBuilder s2 = new StringBuilder(s1);

        reverse(s2);

        return s1.toString().equals(s2.toString());
    }

    static void reverse(StringBuilder s){
        int start=0,end=s.length()-1;