"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.
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.
O(n) time without extra memory.
深刻体会到了英文的用处。。。题目的中文翻译真是误导人。
1 public class Solution { 2 /** 3 * @param s A string 4 * @return Whether the string is a valid palindrome 5 */ 6 public boolean isPalindrome(String s) { 7 char[] cs = s.toCharArray(); 8 int i = 0; 9 int j = cs.length - 1; 10 11 while(i<j) { 12 while(i<j && !Character.isDigit(cs[i]) && !Character.isLetter(cs[i])) i++; 13 while(i<j && !Character.isDigit(cs[j]) && !Character.isLetter(cs[j])) j--; 14 if(i >= j) break; 15 String ss = cs[i] + ""; 16 String ss1 = cs[j] + ""; 17 if(!ss.equalsIgnoreCase(ss1)) 18 return false; 19 20 i++; 21 j--; 22 } 23 return true; 24 } 25 }
原文：http://www.cnblogs.com/FJH1994/p/5023763.html
