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public class ValidPalindrome {
public boolean isPalindrome(String s) {
if (s == null || s.trim().isEmpty()) {
return true;
}
s = s.trim().toLowerCase();
int i = 0;
int j = s.length() - 1;
while (i < j) {
while (i < s.length() && !isValid(s.charAt(i))) {
i++;
}
while (j >= 0 && !isValid(s.charAt(j))) {
j--;
}
if (i < s.length() && j >= 0 && s.charAt(i) != s.charAt(j)) {
return false;
} else {
i++;
j--;
}
}
return true;
}
private boolean isValid(char c) {
boolean isNumber = c >= '0' && c <= '9';
boolean isLetter = c >= 'a' && c <= 'z';
return isNumber || isLetter;
}
}
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