题目：

题解：

bool isalumn(char c) {
    return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9');
}

bool isPalindrome(char* s) {
    for (int left = 0, right = strlen(s) - 1; left < right; left++, right--) {
        while (left < right && !isalumn(s[left])) {
            left++;
        }
        while (left < right && !isalumn(s[right])) {
            right--;
        }
        if (tolower(s[left]) != tolower(s[right])) {
            return false;
        }
    }
    return true;
}