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.
C++
class Solution { bool isAlphaNum(char &ch) { if (ch >= 'a' && ch <= 'z') return true; if (ch >= 'A' && ch <= 'Z') return true; if (ch >= '0' && ch <= '9') return true; return false; } public: bool isPalindrome(string s) { int left = 0, right = s.size() - 1 ; while (left < right) { if (!isAlphaNum(s[left])) ++left; else if (!isAlphaNum(s[right])) --right; else if ((s[left] + 32 - 'a') 2 != (s[right] + 32 - 'a') % 32) return false; else { ++left; --right; } } return true; } bool isPalindrome2(string s){ if("" == s) return true; int left = 0; int right = s.size() - 1; while (left<right){ if(!isAlphaNum(s[left])) left++; else if (!isAlphaNum(s[right])) right--; else if ((s[left] + 32 - 'a') 2 != (s[right] + 32 - 'a') % 32) return false; else { left++; right--;} } return true; } };
转载于:https://www.cnblogs.com/vercont/p/10210242.html
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