125. Valid Palindrome (Easy)
https://leetcode.com/problems/valid-palindrome/
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:
Input: "A man, a plan, a canal: Panama" Output: true
Example 2:
Input: "race a car" Output: false
Solutions
class Solution {
public boolean isPalindrome(String s) {
if (s == null || s.length() <= 1) {
return true;
}
s = s.toLowerCase();
String tmp = "";
for (int i = 0; i < s.length(); i++) {
if ((s.charAt(i) >= 'a' && s.charAt(i) <= 'z') || (s.charAt(i) >= '0' && s.charAt(i) <= '9')) {
tmp += s.charAt(i);
}
}
int left = 0;
int right = tmp.length() - 1;
while (left < right) {
if (tmp.charAt(left) != tmp.charAt(right)) {
return false;
}
left++;
right--;
}
return true;
}
}