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?
bool isPalindrome(int x) { // time: O(logx); space: O(1)
if (x < 0) return false;
int orig = x;
long num = 0;
while (x) {
num = num * 10 + x % 10;
x /= 10;
}
return orig == num;
}