​LeetCode刷题实战125：验证回文串

示例 1:

输入: "A man, a plan, a canal: Panama"
输出: true

示例 2:

输入: "race a car"
输出: false

public boolean isPalindrome(String s) {
   if (s.isEmpty())
       return true;

   int begin = 0;
   int end = s.length() - 1;

   char beginChar, endChar;

   while (begin <= end){
       beginChar = s.charAt(begin);
       endChar = s.charAt(end);
       if (!Character.isLetterOrDigit(beginChar)){
           begin++;
           continue;
       }
       else if (!Character.isLetterOrDigit(endChar)){
           end--;
           continue;
       }
       else {
           if (Character.toLowerCase(beginChar) != Character.toLowerCase(endChar))
               return false;
           else{
               begin++;
               end--;
           }
       }
   }

   return true;
}