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leetcode题解：Valid Palindrome（判断回文）

2024-07-11 00:22:47   220人阅读

题目：

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.

说明：

       1）注意两点：a、判断满足条件的字符  b、大写变小写（本题认为不区分大小写）

       2）字符串为空则true

实现：

 1 class Solution { 2 public: 3         bool isPalindrome(string s) { 4             if(s.empty()) return true; 5             int len=strlen(s.c_str()); 6             int i=0; 7             int j=0; 8             for (;i<len;i++) 9             {10                 if (isChar(s[i]))//去其他符合，若有大写则大写变小写11                 {12                     s[i] = tolower(s[i]);//库函数13                     s[j++]=s[i];14                 }15             }16             s[j]=‘\0‘;17             if (s[0]==‘\0‘) return true;18             int len2=strlen(s.c_str());19             i=0;20             while(i<=len2-1-i) //判断是否回文21             {22                 if(s[i]!=s[len2-1-i]) return false;23                 i++;24             }25             return true;            26     }27     private:28         bool isChar(char t)//判断是否满足条件字符29         {30             if ((‘a‘ <= t&&t<=‘z‘)||(‘A‘ <= t&&t<=‘Z‘)||(‘0‘ <= t&&t<=‘9‘))31            {32                return true;33            }34            else35                return false;           36         }37 };

 

 


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