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.
思考：注意判断语句是否正确。
- class Solution {
- public:
- bool isPalindrome(string s) {
- int len=s.size();
- if(len==0||len==1) return true;
- int i=0,j=len-1;
- while(i<=j)
- {
- if((s[i]<'a'||s[i]>'z')&&(s[i]<'A'||s[i]>'Z')&&(s[i]<'0'||s[i]>'9')) i++;
- else if((s[j]<'a'||s[j]>'z')&&(s[j]<'A'||s[j]>'Z')&&(s[j]<'0'||s[j]>'9')) j--;
- else if(s[i]!=s[j]&&(s[i]-s[j]!='A'-'a')&&(s[i]-s[j]!='a'-'A')) return false;
- else
- {
- i++;
- j--;
- }
- }
- return true;
- }
- };