描述 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.
分析 將字符串轉(zhuǎn)換為小寫格式，便于統(tǒng)一比較。 自動跳過非數(shù)字字母的字符。
代碼
class Solution {public: bool isPalindrome(string s) { transform(s.begin(), s.end(), s.begin(), ::tolower); auto left = s.begin(), right = prev(s.end()); while (left < right) { if (!::isalnum(*left)) ++left; else if (!::isalnum(*right)) --right; else if (*left != *right) return false; else { ++left; --right; } } return true; }};新聞熱點
疑難解答
