Difficulty
Easy
Description
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
Time Complexity: O(log(x))
Space Complexity: O(1)
class Solution {
public boolean isPalindrome(int x) {
if (x < 0)
return false;
if (x == 0)
return true;
int rev = 0;
int ori = x;
while (x != 0) { //翻转数字判断
if (rev > Integer.MAX_VALUE/10 || (rev == Integer.MAX_VALUE/10 && x % 10 > 7))
return false;
rev = rev * 10 + x % 10;
x /= 10;
}
return rev == ori ? true : false;
}
}