Description
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
Note: For the purpose of this problem, we define empty string as valid palindrome.
Example
Example 1:
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| Input: "A man, a plan, a canal: Panama"
Output: true
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Example 2:
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| Input: "race a car"
Output: false
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Solution
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| class Solution {
public boolean isPalindrome(String s) {
if (s.isEmpty()) {
return true;
}
int head = 0, tail = s.length() - 1;
char cHead, cTail;
while(head <= tail) {
cHead = s.charAt(head);
cTail = s.charAt(tail);
if (!Character.isLetterOrDigit(cHead)) {
head++;
} else if(!Character.isLetterOrDigit(cTail)) {
tail--;
} else {
if (Character.toLowerCase(cHead) != Character.toLowerCase(cTail)) {
return false;
}
head++;
tail--;
}
}
return true;
}
}
|