【英文】验证回文串

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Preface

LeetCode solution, language Java

Problem

Source Code

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class Solution {
    public boolean isPalindrome(String s) {

        // Convert all characters to lowercase
        s = s.toLowerCase();

        // Remove non-lowercase letters and non-digits
        String str = new String();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i)>=97 && s.charAt(i)<=122) {
                str += s.charAt(i)+"";
            } else if (s.charAt(i)>=48 && s.charAt(i)<=57) {
                str += s.charAt(i)+"";
            }
        }

        /*
            Algorithm: Check if it is a palindrome
            Create a flag, which is set to true by default, indicating it is a palindrome
            If there is any non-palindrome condition in the loop, set the flag to false
            After the loop, if no non-palindrome condition is found, the flag remains true (default)
         */
        boolean flag = true;
        for (int i = 0; i < str.length()/2; i++) {
            if (!(str.charAt(i)+"").equals(str.charAt(str.length()-(1+i))+"")) {
                flag = false;
            }
        }

        return flag;
    }

}

Completion