> For the complete documentation index, see [llms.txt](https://liuyang89116.gitbook.io/my-leetcode-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuyang89116.gitbook.io/my-leetcode-book/post_chapter_2_math/problem_9_palindrome_number.md).

# Problem 9: Palindrome Number

> <https://leetcode.com/problems/palindrome-number/>

## 思路

![](/files/-Lpv9zSYkjB4p5ug_NKL)

```java
public class Solution {
    public boolean isPalindrome(int x) {
        if (x < 0) {
            return false;
        }

        int div = 1;
        while (x / div >= 10) {
            div *= 10;
        }
        while (x != 0) {
            int left = x / div; // get highest pos;
            int right = x % 10; // git lowest pos;
            if (left != right) {
                return false;
            }

            x = (x % div) / 10;
            div = div / 100;
        }

        return true;
    }
}
```

## 易错点

1. 去掉头再去掉尾

   ```java
   x = (x % div) / 10; // x % div 去掉了头，除以10　去掉尾
   ```

   ２. div 除以 100，因为 ｘ 去掉了两位　


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