文章--LeetCode算法--TwoSumPalindromeNumbe
PalindromeNumber
问题描述
Determine whether an integer is a palindrome. Do this without extra space.
Could negative integers be palindromes? (ie, -1)
If you are thinking of converting the integer to string, note the restriction of using extra space.
You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed
integer might overflow. How would you handle such case?
There is a more generic way of solving this problem.
实例
- 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.
实现代码
public class Solution {
public boolean isPalindrome(int x) {
if (x < 0 || (x != 0 && x % 10 == 0))
return false;
int rev = 0;
while (x > rev) {
rev = rev * 10 + x % 10;
x = x / 10;
}
return (x == rev || x == rev / 10);
}
}