LeetCode:Valid Palindrome

Posted 2020-07-21 walker lee

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.

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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;
    }
};