1.Determine whether an integer is a palindrome. Do this without extra space.
Some hints:
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.
2.题目要求：验证回文字符串。
3.方法：利用取整和取余来获得我们想要的数字，比如 1221 这个数字，如果 计算 1221 / 1000， 则可得首位1， 如果 1221 % 10， 则可得到末尾1，进行比较，然后把中间的22取出继续比较。
4.代码：
class Solution {
public: bool isPalindrome(int x) {
if (x < 0)
return false;
int div = 1;
while (x / div >= 10)
div *= 10; while (x > 0) {
int left = x / div;
int right = x % 10;
if (left != right)
return false;
x = (x % div) / 10;
div /= 100;
}
return true;
}
};
