125. Valid Palindrome【easy】
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.
解法一：
1 class Solution { 2 public: 3 bool isPalindrome(string s) { 4 int start = 0, end = s.length() - 1; 5 while (start <= end) { 6 if (!isalnum(s[start])) { 7 start++; 8 } else if (!isalnum(s[end])) { 9 end--; 10 } else { 11 if (tolower(s[start++]) != tolower(s[end--])) { 12 return false; 13 } 14 } 15 } 16 return true; 17 } 18 };
原文：http://www.cnblogs.com/abc-begin/p/7581389.html