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125. Valid Palindrome
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125. Valid Palindrome
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/***************************************************
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
Given a string s, return true if it is a palindrome, or false otherwise.
Example 1:
Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.
Example 2:
Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.
Example 3:
Input: s = " "
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.
Constraints:
1 <= s.length <= 2 * 105
s consists only of printable ASCII characters.
Accepted
1.8M
Submissions
4.1M
Acceptance Rate
44.2%
************************************************
class Solution {
public:
bool isPalindrome(string s) {
int left=0; int right=s.length()-1;
while(left<right){
if(!isalnum(s[left])){
left++;
}
else if(!isalnum(s[right])){
right--;
}
else if(tolower(s[left++])!=tolower(s[right--])){
return false;
}
}
return true;
}
};