2017/3/15 21:47:04
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome.
Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.
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publicclassSolution{publicboolean isPalindrome(String s){for(int i=0,j=s.length()-1;i<j;)if(Character.isLetterOrDigit(s.charAt(i))&&Character.isLetterOrDigit(s.charAt(j)))if(Character.toLowerCase(s.charAt(i))!=Character.toLowerCase(s.charAt(j)))returnfalse;else{ i++;j--;}elseif(!Character.isLetterOrDigit(s.charAt(i))) i++;elseif(!Character.isLetterOrDigit(s.charAt(j))) j--;returntrue;}}publicclassSolution{publicboolean isPalindrome(String s){for(int i=0,j=s.length()-1;i<j;)if(Character.isLetterOrDigit(s.charAt(i))&&Character.isLetterOrDigit(s.charAt(j))){if(s.charAt(i)== s.charAt(j)||(s.charAt(i)>64&& s.charAt(j)>64&&Math.abs(s.charAt(i)- s.charAt(j))==32)){i++;j--;continue;};returnfalse;}elseif(!Character.isLetterOrDigit(s.charAt(i))) i++;elseif(!Character.isLetterOrDigit(s.charAt(j))) j--;returntrue;}}publicclassSolution{publicboolean isPalindrome(String s){String actual = s.replaceAll("[^A-Za-z0-9]","").toLowerCase();returnnewStringBuffer(actual).reverse().toString().equals(actual);}}原文：http://www.cnblogs.com/flyfatty/p/6624794.html