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Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

Input: 121Output: true

Example 2:

Input: -121Output: falseExplanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.

Example 3:

Input: 10Output: falseExplanation: 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?

题意：判断一个整型数据是否是一个回文数。

思路1：可以转换为字符串，然后 reverse 和原串对比。代码：

class Solution {
   public:    bool isPalindrome(int x) {
           string s = to_string(x), t = s;        reverse(t.begin(), t.end());         return s == t ? true : false;    }};

思路2：将原数值转为新的回文数值，然后对比。注意，转换过程中可能出现溢出，因此使用 long long 。另外，负数一定不是回文数。代码：

class Solution {
   public:    bool isPalindrome(int x) {
            if (x < 0) return false;         else {
               long long rev = 0, t = x;            while (t) {
                   rev = rev * 10 + t % 10;                t /= 10;            }            return x == rev ? true : false;        }    }};

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