Palindrome Number
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.
最简单的方法，逆转数字，本来想用数字逆转后一半进行判断，发现边界条件太多，觉得不值得做。
Runtime: 131 ms
class Solution { public: bool isPalindrome(int x) { long long reverseX = 0, oriX = x,temp; if (x < 0){ oriX = oriX*-1; return false; } temp = oriX; while (oriX > 0){ reverseX = reverseX * 10 + oriX % 10; oriX = oriX / 10; } oriX = temp; while (oriX > 0){ if (oriX % 10 == reverseX % 10){ oriX = oriX / 10; reverseX = reverseX / 10; } else{ return false; } } return true; } };
原文：http://www.cnblogs.com/JeromeHuang/p/4445052.html