題目：

題解：

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;
}