LeetCode每日一题：palindrome number

问题描述

Determine whether an integer is a palindrome. Do this without extra space.
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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.

问题分析

这题要求不使用额外空间，所以无法使用栈或者转化成字符串求解，正确的做法是不断掐头去尾，比较是否相同。

代码实现

public boolean isPalindrome(int x) {
        if (x < 0)
            return false;
        int div = 1;
        while (div <= x / 10)
            div *= 10;
        while (x > 0) {
            if (x / div != x % 10)
                return false;
            x = (x % div) / 10;
            div /= 100;
        }
        return true;
    }