LeetCode 125. Valid Palindrome

125. Valid Palindrome

My Submissions QuestionEditorial Solution

Total Accepted: 99300 Total Submissions: 417275 Difficulty: 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.

class Solution {
public:
bool isPalindrome(string s) {
if(s.length() == 0)
return true;
int i = 0, j = s.length() - 1;
while(i < j) {
while(i < j && !isalnum(s[i])) {
i++;
}
while(i < j && !isalnum(s[j])) {
j--;
}
if(i < j && tolower(s[i]) != tolower(s[j])) {
return false;
} else {
i++;
j--;
}
}
return true;
}
};