Valid Palindrome

最新推荐文章于 2024-01-04 12:53:14 发布

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本文介绍了一种使用双指针技术来判断字符串是否为回文的方法，特别关注于只考虑字母和数字字符的情况，并忽略大小写差异。通过示例说明了算法的工作原理。

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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.

用两个指针向内对比，注意大小写的问题。

class Solution {
public:
    bool isPalindrome(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        if(s.length() == 0) return true;
        
        int i = 0,j = s.length() - 1;
        
        while(i < j)
        {
            while(!isalnum(s[i]) && i < j ) i++;
            if(i==j) return true;
            
            while(!isalnum(s[j])) j--;
            if(i>=j) return true;
            
            if(tolower(s[i++]) != tolower(s[j--])) return false;
        }
        return true;
    }
};

52 milli secs