LeetCode [125] Valid Palindrome

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:

Input: "race a car"
Output: false

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class Solution { bool isValid(char c){ return (c>='a'&&c<='z')||(c>='A'&&c<='Z')||isdigit(c); } bool isEqual(char a, char b){ int diff = abs('a'-'A'); return a==b||(!isdigit(a)&&!isdigit(b)&&abs(a-b)==diff); } public: bool isPalindrome(string s) { int n = s.size(), i = 0, j = n-1; while(i<=j){ if(!isValid(s[i])){ i++; }else if(!isValid(s[j])){ j--; }else if(isEqual(s[i], s[j])){ i++; j--; }else{ return false; } } return true; } };

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class Solution { #define isA(c) ((c>='a'&&c<='z')||(c>='A'&&c<='Z')) #define isAN(c) (isA(c)||(c>='0'&&c<='9')) #define isEqual(c1,c2) (isA(c1)&&isA(c2)&&abs(c1-c2)==32||c1==c2) public: bool isPalindrome(string s) { int n = s.size(), l = 0, r = n-1; while(l<r){ while(l<r && !isAN(s[l])) l++; while(l<r && !isAN(s[r])) r--; if(l<r && !isEqual(s[l], s[r])) return false; l++; r--; } return true; } };