9. Palindrome Number
Tags: ‘Math’
Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
Example 1:
Input: 121 Output: true
Example 2:
Input: -121 Output: false Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
Example 3:
Input: 10 Output: false Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
Follow up:
Coud you solve it without converting the integer to a string?
Solution
方法1: Naive way O(n) time O(n) space
public boolean isPalindrome(int x) {
String s = String.valueOf(x);
int i = 0, j = s.length() - 1;
while (i < j) {
if (s.charAt(i++) != s.charAt(j--)) {
return false;
}
}
return true;
}