LeetCode-E-Valid Palindrome

題意

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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解法

遍歷

實現

bool isAlphanumeric(char ch){
        if(ch >= 'a' && ch <= 'z' || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9')) return true;
        return false;
    }

    bool isPalindrome(string s) {
        int i = 0, j = s.size() - 1;
        while(i <= j){
            if(!isAlphanumeric(s[i])){
                ++i;
                continue;
            }else if(!isAlphanumeric(s[j])){
                --j;
                continue;
            }else{
               if(tolower(s[i]) != tolower(s[j])) return false;
               ++i;
               --j;
            }
        }
        return true;
    }