Difficulty: Easy
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 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
Language: Java
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class {
public boolean isPalindrome(String s) {
if (s == null || s.length() == 0) {
return true;
}
int left = 0;
int right = s.length() - 1;
while (left < right) {
while (left < right && !Character.isLetterOrDigit(s.charAt(left))) {
left++;
}
while (left < right && !Character.isLetterOrDigit(s.charAt(right))) {
right--;
}
if (left < right) {
if (Character.toUpperCase(s.charAt(left)) != Character.toUpperCase(s.charAt(right))) {
return false;
} else {
left++;
right--;
}
}
}
return true;
}
}
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