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：
class Solution {
public:
bool isPalindrome(string s) {
int start = , end = s.length() - ;
while (start <= end) {
if (!isalnum(s[start])) {
start++;
} else if (!isalnum(s[end])) {
end--;
} else {
if (tolower(s[start++]) != tolower(s[end--])) {
return false;
}
}
}
return true;
}
};