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Valid Palindrome

2024-07-18 11:50:47   225人阅读

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.

 

这题直接在头尾设置两个指针，同时向中间扫面，每扫到一个数字或字母就停下来，比较是否相等，若不等就不是回文。代码如下：

 

 1 class Solution { 2 public: 3     bool isPalindrome(string s) { 4         if( s.empty() ) return true; 5         int left = 0; 6         int right = s.length() - 1; 7         while( left < right ) { 8             while( left < right && !isalnum(s[left]) ) ++left;  //从左往右寻找alpha num  9             while( left < right && !isalnum(s[right]) ) --right;    //从右往左寻找alpha num10             if( left < right && tolower(s[left]) != tolower(s[right]) ) return false;   //在忽略大小写的情况下，如果不等，则不是回文11             ++left;12             --right;13         }14         return true;15     }16 };

 

 

 


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