valid-palindrome

Valid Palindrome – LeetCode 125

Problem

Description

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

Answer

Original

Code

class Solution {
public:
    bool isPalindrome(string s) {
        for (int i = 0, j = s.size() - 1; i < j; i++, j--) { 
            while (isalnum(s[i]) == false && i < j) i++; 
            while (isalnum(s[j]) == false && i < j) j--; 
            if (toupper(s[i]) != toupper(s[j])) return false; 
        }
    return true;
    }
};

思路

简单的头尾同时遍历比对，时间复杂度$O(n)$，空间复杂度$O(1)$。

Better

思路

没看到更好的