# 9 Palindrome Number – Easy

### Problem:

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.

### Thoughts:

This question is not very interesting. The requirement “without extra space” is kind of tricky to understand. Maybe it’s trying to say if the number is n digit long, solve it with O(1) space instead of O(n) space.

### Solutions:

```java
public class Solution {
    public boolean isPalindrome(int x) {
        if (x < 0) {
            return false;
        }
        int left = 1;
        while (x / left >= 10) {
            left = left * 10;
        }
        int right = 1;
        while (left > right) {
            if ((x / left) % 10 != (x / right) % 10 ) {
                return false;
            }
            left = left / 10;
            right = right * 10;
        }
        return true;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ugopireddy.gitbook.io/leet-code-solutions/solutions_1_-_50/9_palindrome_number__easy.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.