LeetCode:Valid Palindrome

Valid Palindrome

Total Accepted: 103983  Total Submissions: 432738  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.

Subscribe to see which companies asked this question

Hide Tags

  Two Pointers String

Hide Similar Problems

  (E) Palindrome Linked List

c++ code:

class Solution {
public:
    bool isPalindrome(string s) {
        
        if(0 == s.size()) return true;
        int i=0,j=s.size()-1;
        while(i<=j){
            while(!isA(s[i]) && i<j) i++;
            while(!isA(s[j]) && i<j) j--;
            if(tolower(s[i])!=tolower(s[j]))
                return false;
            i++;j--;
        }
        return true;
    }
    bool isA(char c){
        if('a'<=c && c<='z' || 'A'<=c && c<='Z' || '0'<=c && c<='9')
            return true;
        else
            return false;
    }
};